It's All Relative - Thinkers and Talkers

Jen plays in a rock band that’s really hot right now.

à (The band) It’s really hot right now.

à SOMETHING: use that or which

à The band is the subject in the second part of the sentence

Nina is an interesting woman who sits across from me at work.

à (Nina) She sits across from me at work.

à SOMEONE: use who or that

à Nina is the subject in the second part of the sentence

She’s a new friend (who/that) I met through Mike.

à (She) I met her through Mike.

à SOMEONE: use nothing, who or that

à She is the object in the second part of the sentence

It’s a new band (which/that) Jen started.

à (A new band) Jen started it.

à SOMETHING: use nothing, which or that

à A new band is the object in the second part of the sentence

Note: Object and Subject

Pra quem não lembra das aulas de português, sujeito (subject) é quem executa a ação representada pelo verbo na frase (embora nem todo verbo necessariamente indique uma ação, essa é uma maneira simples de você entender a coisa) e objeto (object) é quem sofre a ação executada pelo sujeito.

Jack ate a Big Mac this morning. subject: Jack / object: Big Mac