Verbs: Bí → “To be” VS Copail → “To be”

I am a girl, I am a boy, I am tall, I am short - how do you talk, describe or introduce something/someone in Irish? There are two verbs used in Irish, Bí and Copail, both of which are verbs for "to be". The following are their conjugations:

Bí (to be):

I am: taím/tá mé

You are (singular) : tá tú

He/it is: tá sé

She/it is: tá si

You (plural) are: tá sibh

They are: tá siad

We are: táimid/tá muid

Copail (to be):

I am (x) :  is (x) mé

You are (x) (singular): is (x) tú

He/it is (x): is (x) sé

She/it is: is (x) si

You (plural) are: tá sibh

They are (x) : is (x) iad

We are (x) : is (x) muid/ is (x) sinn

What is the difference between the two?

Bí is used when you're describing the characteristics of a a person or things, such as "Tá sé ard" (He is tall). “Copail”, on the other hand, is used when you're introducing a person or thing, such "Is cailín sí" (She is a girl) or "Is cota sé" (It is a coat).