A correction has been made in this story. See below for details.

To shoppers, a deal often means a good price. But the hot space in retail right now is wheeling and dealing -- snatching up startups.

E-commerce has been the most active segment in digital media and advertising mergers and acquisitions thus far in 2011, with 67 transactions topping $6 billion so far, according to investment bank Petsky & Prunier, which specializes in the sector. That far outpaces last year's $180 million in activity for the same period.

"What's most interesting is now you see offline and traditional retailers move into the e-commerce sector," said Bob Ennis, managing director of Petsky. "Big , well-capitalized companies are recognizing that e-commerce is becoming indistinguishable from commerce, period."

The entire retail category is driving toward segments such as mobile, tablets and social media -- leading to a veritable alphabet soup of new sales channels, from m-commerce to t-commerce to s-commerce and even f-commerce (that 's mobile, tablet, social and Facebook commerce, for the uninitiated). Here's a primer.

M- & T-COMMERCE
As more and more smartphones hit the market -- 72.5 million Americans over 13 are toting them, according to ComScore -- phones are becoming shopping assistants, marketing and loyalty tools, a portal to online purchases and a replacement for consumers' wallets.

Consumers are already spending on their mobile devices. Mobile shopping, excluding travel in the U.S., doubled last year to more than $3.4 billion, according to ABI Research, while travel purchases add another $1.5 billion. Already eBay is seeing significant revenue from mobile, with sales of $2 billion in 2010, more than triple 2009 levels.

And it's not just phones. Many retailers report that half of what they consider to be mobile traffic comes via tablets, according to a Forrester Research report. Tablets (t-commerce) are expected to be a big driver of mobile commerce because they are better-suited to browsing, and will likely steal share from desktop- or laptop-based shopping, wrote Forrester principal analyst Sucharita Mulpuru.

Still, mobile has sidled up to the in-store experience as a shopping aid or way for customers to find products or services in proximity. That's why ^*eBay snapped up barcode-scanning app Red Laser, after consumers flocked to the app to price-compare in stores. Then eBay scooped up location-based service Where, which helps consumers find the products and services closest to where they're standing. Groupon, which popularized daily group deals, has also begun making moves toward a mobile app. After acquiring mobile developer Mob.ly last year, it's since launched Groupon Now. The app helps consumers find activities or meals in an instant when they, say, walk out the door of their office, looking for a lunch spot. Groupon has also purchased an early Foursquare competitor, Whrrl, to layer customer loyalty into its mobile services. "It plays perfectly to mobile: anywhere, anytime I can react, which a PC can't do," said Mark Beccue, senior analyst for ABI Research. "It's the impulse buy on steroids."

The latest frontier in the category is mobile wallets, which has tech companies such as Google, as well as credit-card companies and wireless carriers, scrambling to be first. Google is shipping phones with chips that allow touch-to-pay, and it acquired mobile-payments firm Zetawire to enable entirely mobile-based transactions with select bank- and credit-card partners.

F- & S-COMMERCE
Consumers' ability to share items and opinions with friends, as well as buy directly on sites where they already spend time socializing, has caught retailers' attention. In total, Americans spent the equivalent of more than 100 years (53 million minutes) on Facebook during March, according to ComScore.

Express, JCPenney, Walmart and 1-800 Flowers are just a few of the companies seeing big opportunity in social commerce. Express called s-commerce the "next step in our evolution as a retailer" when it announced earlier this month that its full product assortment would be available on Facebook. And Walmart cited the influence of social networking on shopping habits when it purchased Kosmix, a social-media filter.

Still, in a recent Booz & Co. report, the firm called the market for s-commerce "embryonic" but rapidly evolving, estimating that revenue from s-commerce will reach $30 billion globally in the next five years. A 2010 survey by the firm found that 27% of those who had spent at least one hour a month on social-networking sites and had bought at least one product online in the previous year would be willing to purchase physical goods via a social-networking site.

Some such as 1-800Flowers.com and Shoebuy.com are also seeing success in tempting consumers with virtual goods. IFeelGoods, for example, has run promotions with both retailers offering Facebook Credits in lieu of traditional discounts or coupons. In one such program, 1-800Flowers offered consumers 50 Facebook Credits -- the equivalent of $5 -- and logged 4,000 transactions.

But despite the enthusiasm of some, others are increasingly skeptical about Facebook's potential to drive e-commerce. Forrester recently published a report acknowledging the "few pockets of success" but calling Facebook's ability to drive revenue "elusive" and saying that the site is "unlikely to correlate directly to near-term sales."

CPG E-COMMERCE
Major players are also waking up to the potential of packaged-goods e-commerce. In recent months, the likes of Walgreens and Amazon have bought their way further into the space with the purchase of Drugstore.com and Quidsi -- owner of Diapers.com, Soap.com and BeautyBar.com -- respectively.

Amazon's deal highlighted the potential for selling consumer staples online. Household products, like toilet paper, shampoo and cleaning supplies, account for a small but rapidly growing slice of online sales. Last year, online sales of such products were nearly $10 billion, up from $4 billion in 2003, according to Nielsen.

Likewise, Walgreens has been working to strengthen its e-commerce and mobile-commerce offerings, as well as get a leg up on competitors CVS and Rite Aid.

"Our acquisition of Drugstore.com today significantly accelerates our online strategy," Greg Wasson, president-CEO of Walgreens, said at the time. "This acquisition offers a unique opportunity that will provide us immediate access to more than 3 million savvy, online loyal customers, and will allow us to move even closer to our existing customers through relationships with new vendors and partners, adding approximately 60,000 products to our already strong online offering."

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CORRECTION: An earlier version of this story said Amazon, and not eBay, acquired barcode-scanning app Red Laser.