οτι has the following uses (see GGBB page 748 or any of the lexicons):
A content οτι - In this use, οτι introduces the content of what is said, thought, perceived, remembered, known, sworn, etc.
Causal - In this usage, the οτι is a DMW for an adverbial, dependent clause showing cause.
Direct discourse - Here the οτι is introducing direct discourse and can be translated with a set of quotation marks.
Apposition - Here the οτι introduces a word, phrase, or clause that is in apposition to some other noun.