Item means an individual article or unit, especially one that is part of a collection, list or set. For example "the items on the agenda".
Some synonyms for item are: thing, object, unit, article, module, artefact, commodity, piece, product or bit. Item can also mean a piece of news or information or an entry in an account.
The word started out as the Latin term for "also", "in the same manner", and it got its present English meaning from a misunderstanding when it was used in lists. The first entry in the list would begin "In primis" (firstly"), and then the other entries with "Item" (Latin for "also").