They've agreed to join us.
- We got word from our friends. They've agreed to join us. / Мы получили известия от наших друзей. Они согласились к нам присоединиться.
That's them.
- Is that them? / Это они?
- That's them. / Это они.
They were just leaving.
- How long will you guests be staying here? / Сколько здесь еще пробудут твои гости?
- They were just leaving. / Они как раз уходят.
They play ice-hockey. (постоянно)
They're playing ice-hockey. (в данный момент)
They should be here any second.
They've agreed to join us.
They don't even speak English.