Truncation literally means "cutting short." It allows you to put in part of a word and retrieve all the forms of the word that start with the characters you have entered. The most common symbol used for truncation is an *, but like the wildcard it may be different in different databases. Unlike the wildcard (which replaces a single letter and can be used in the middle or end of a word), Truncation can allow any number of letters and only works at the end of the word.
archit* retrieves architecture or architect
psycho* retireves psychosis, psychotic, etc.
Be careful not to over use truncation; many times if you cut a word too short you will get words that don't actually relate.
consum* retrieves consumer, consumes, consumerism
cons* retrieves all those words along with constipation, consult, constituent... etc.