To be able to understand direct pronouns you need to know what a direct object is:
A direct object is the direct recipient of the action of the verb - for example: Legge il libro - the book is the direct object.
Verbs that take a direct object are called transitive verbs.
We use direct objects to replace direct object nouns to avoid repetition in sentences: Lo legge.
Here is a list of the direct pronouns in Italian: mi, ti, la/ lo, ci, vi, li/ le.
They are placed immediately before a conjugated verb - compro la frutta e la mangio.