The base DN for the search
A search filter, specifying criteria an entry must fulfill to match.
Scope of the search, either look at the base DN only, only look one level below it, or look at the whole subtree rooted at the base DN.
Size limit of at most how many matching entries to return.
Attributes to return, or none for all attributes the matching entries happen to have.
An example search filter:
(cn=John Smith)