动词 Ser：

动词 Estar：

动词：Ter

Ser is used to say when you are something (inherent characteristic), and estar is used to say when you are in/at somewhere (location):

Eu sou o novo aluno.     I am the new student.
Eu estou no meu novo carro.     I am in my new car.

Many common expressions that use the verb be in English use the verb ter in Portuguese:

to be afraid - ter medo
to be against - estar contra
to be at fault - ter culpa
to be careful - ter cuidado
to be cold - estar com frio
to be curious - ser curioso/a
to be happy - estar contente
to be hot - estar com calor
to be hungry - estar com fome
to be in a hurry - ter pressa, estar com pressa
to be jealous - ter ciúmes
to be lucky - ter sorte
to be patient - ser paciente
to be successful - ter sucesso
to be thirsty - estar com sêde
to be tired - estar cansado/a