A BASIC Stamp is a single-board computer that runs the Parallax PBASIC language interpreter in its microcontroller. The developer's code is stored in an EEPROM, which can also be used for data storage. The PBASIC language has easy-to-use commands for basic I/O, like turning devices on or off, interfacing with sensors, etc. More advanced commands let the BASIC Stamp module interface with other integrated circuits, communicate with each other, and operate in networks. The BASIC Stamp microcontroller has prospered in hobby, lower-volume engineering projects and education due to ease of use and a wide support base of free application resources.
What about the other companies that sell a "BASIC Stamp clone" for less? If you've looked into other products that compare themselves to the BASIC Stamp microcontroller dig a little deeper before you get out your credit card. There's much more to buying a product like a BASIC Stamp module than a feature list could possibly demonstrate. Ask about support documentation, user base, reliability and track record in industrial applications, returns, free technical support, customer service and everything else that matters (mostly after the package has arrived!).