AuthenTec makes fingerprint sensor chips that are used in computers made by Lenovo, Fujitsu, and Dell, and also makes security software and chips for mobile phones that are licensed to companies like Samsung. The company also developed a downloadable digital rights management solution that is used on the iPhone and iPad to authenticate HBO GO.
In addition to those products, AuthenTec also produces chips for near-field communication (NFC), a technology that is used for secure wireless transactions. NFC payment capabilities are already built in to some Android phones via Google Wallet, and the technology is expected to make an appearance in a future iPhone (even if it's not the next iPhone).
As with all such acquisitions made by Apple, these capabilities don't necessarily indicate that a specific technology is going to appear in Apple products in the near term. However, Apple's acquisitions strategy is aimed at helping the company control technologies that it sees as essential to its business, so there's something in AuthenTec's portfolio or someone among its personnel that's key to Apple's plans. Larry Dignan at ZDnet suggests that AuthenTec's purchase is a move to fend off Samsung and to enhance Apple's attractiveness in the enterprise space, where many companies are moving to a bring your own device (BYOD) model.