Try having a quick search of the forum or google for that matter. After 30 secs worth of searching I found:
"Test beds are the environments in which the standard tasks may be implemented. In addition to the environment itself, these tools provide a method for data collection, the ability to control environmental parameters, and scenario generation techniques. The purpose of a test bed is to provide metrics for evaluation (objective comparison) and to lend the experimenter a fine-grained control in testing agents."
<font size="2" face="Verdana, Arial, Helvetica">Isn't that when you go into a furniture shop & bounce up & down on a few beds to see how comfortable they are... [img]images/icons/wink.gif[/img]
But seriously, the first response is pretty generous. I wish mine was that good. My definition is more like:
"a malleable environment structure which provides interchangeable combinations of operating environments in which to exercise the AUT and into which established entry/exit criteria datasets may be inserted seamlessly for consistent test suite execution & evaluation of success criteria independent of the current testbed configuration."