This Tense is used to express an action which is over just now or completed today. In this tense the third form of the verb is used.
The formula for present perfect is Subject +Auxiliary Verb + V3 (Past Participle Form)
I have eaten an apple today.
We have eaten apples today.
We have eaten apples today.
You have eaten an apple today.
He has eaten an apple today.
She has eaten an apple today.
It has eaten an apple today.
They have eaten apples today.