Conceptual shorthand for the tendency of the human mind to expect certain things in certain situations (
schemata), or expect certain things to follow each other in series(
scripts).
For instance, my schema for a kitchen includes a sink, a stove, a fridge, and some dishes. Not only do these things appear in my mind when we hear the word "kitchen," but I will also notice their abscence. If I walked into a kitchen that had no sink, I might notice something was up, even before I said "Hey, there's no sink in here."
Scripts are similar, but involve a sequence of events or actions. My script for entering my apartment building goes something like: Transfer all bags to left hand. Open front door. Get keys out of pocket. Unlock door. Walk to elevator. Push elevator button. (and so on) I can tell this is a script, since I will sometimes get my keys out even if someone is holding the door wide open.
Scripts and schemata can be seen as negative because they are so non-conscious, so automatic. They make it easier to sleepwalk through life. On the other hand, they also allow us to digest situations and perform tasks more quickly. My approach is to be aware of the scripts and schemata I am using.