It means Ser ó Estar, and has three forms : AM / IS / ARE. Remember the Personal Pronouns:
I yo YOU tú HE él
SHE ella IT esto (neutro)
WE nosotr. YOU uds. THEY ellos
THE CONJUGATION
I AM
HE WE
SHE IS YOU ARE
IT THEY
Now we can make sentences
AFFIRMATIVE FORM
N/P + VERB + COMPLEMENT 1.- She is a girl
2.- Peter is a policeman
3.- You are in class
4.- We are happy
5.- They are intelligent boys
NEGATIVE FORM
N/P + VERB + NOT + COMPLEM.
1.- She is not a girl
2.- Peter is not a policeman
3.- You are not in class
4.- We are not happy
5.- They are not intelligent boys
INTERROGATIVE FORM
VERB + N/P + COMPLEMENT
1.- Is She a girl ?
2.- Is Peter a policeman ?
3.- Are You in class ?
4.- Are We happy ?
5.- Are They intelligent boys ?
RECUERDA : También podemos usar el Verbo en contracciones así :
He is not He isn´t
I am not I´m not
You are not You aren´t
NO OLVIDES :Que el Verbo TO BE es la base de la gramática inglesa.
Además debes memorizar los pronombres y las formas del verbo.