The uninflected word іто means 'this/that is'; it is used to make sentences, not to modify nouns. The word ітот is inflected as a special adjective (see Dictionary); it modifies nouns. The form іто is therefore ambiguous:
Јто моё письмћ. This is my letter.
Јто моќ карандашќ. These are my pencils.
Јто письмћ моё This letter is mine.
Јта рџчка мої. This pen is mine.
Јтот карандђш мћй. This pencil is mine.
Јти карандашќ моќ. These pencils are mine.