Fuzzy Matching on terms. At the moment, implemeted with MySQL Natural Language Full-Text Search capability. It's not perfect, but it greatly increases the likelihood of matching. On the down side, it requires still uses case-insensitive exact string matching - i.e. a search for "ascii" would include "flat-ASCII" and "ASCII art", but a search for "ASBII" would not return "ASCII". In the future, I hope to upgrade this to a better algorithm that will cope with spelling errors.
Exact Matching is exact case-insensitive matching. A search for "ascii" would return "ASCII" but not "plain-ASCII" or "ASCII art".
MySQL Wildcards uses MySQL's LIKE comparison and accepts "%" as a wildcard, used like "*". (It also translates "*" to "%" for non-MySQL people.)
Full Text (Not Implemented Yet) will allow a Natural Language Full-Text Search of the full text of entry definitions. (I'm not implementing this yet, as I haven't decided whether I can spare the disk space for indexing the full entry text, or how well it will perform.)