Learn Spanish (Spain): Los lavamos luego. - We are washing them later.

Los means "them". In Spanish, direct object pronouns like lo, la, los, and las are usually placed right before the conjugated verb. So instead of saying "We wash them" like in English, Spanish structures it as "Them we wash" (Los lavamos).

What does "Los" refer to? Can it be people or things?

It can be either! Los replaces any masculine plural noun. It could mean we are washing "them" as in the dishes (los platos), the dogs (los perros), or the cars (los coches). If we were washing feminine things, like the shirts (las camisas), we would use las instead: Las lavamos luego.

Where is the word for "we" in this sentence?

The "we" is built directly into the verb. The -amos ending in lavamos tells us the subject is nosotros (we). You could say Nosotros los lavamos luego, but Spanish speakers usually drop the subject pronoun because the verb makes it completely clear.

The English translation says "we are washing", but isn't "lavamos" the simple present tense?

Yes, lavamos is the simple present tense ("we wash"). However, in Spanish, the simple present is very flexible. It is often used to talk about actions happening right now ("we are washing") or plans in the near future, especially when you include a time word like luego (later).