To avoid repeating the same word over and over again in English, we use words like it and them. For example, I like that shirt. I want it! or Do you like these shoes? I want them!
In Spanish, you can use lo, la, los, or las, depending on the gender and number of the noun.
In English we say I want it, but in Spanish you’d say yo lo quiero. Notice how lo, la, los, and las come before the verb and not after it!