Truncation broadens a search to retrieve items containing various forms of a word.
For example: model* could retrieve model, modelling, modeling, models etc.
Symbols used may be *, $, ?, or # (Database dependent ... PubMed uses * for right-hand truncation and Agricola uses * for either side).
Dangers in using truncation? Yes, shortening the word too much may retrieve too many results - for example, rat* could retrieve ration or rationing, while you are hoping to retrieve anything with Rattus).