Learn Italian: Mi piace il pollo.

In Italian, the verb piacere (to like) works backwards compared to English. It actually translates closer to "to be pleasing to". So, instead of saying "I like chicken", you are literally saying "The chicken is pleasing to me". Since the chicken is doing the "pleasing", the verb is in the "it" form (piace).

What does mi mean in this sentence?

Mi means "to me". Because the Italian sentence is structured as "The chicken is pleasing to me", the word mi handles the "to me" part of the sentence.

Why is there an il before pollo? In English we just say "chicken", not "the chicken".

In Italian, when you talk about a broad category or something you like in general (like chicken, coffee, or dogs), you almost always have to use the definite article (il, la, i, or le). So, "chicken in general" becomes il pollo.

If I wanted to say I like something plural, would I still use piace?

No. Because the thing you like is technically the subject of the sentence, the verb has to match it. If you like something plural (like cats, i gatti), you must use the plural form of the verb, which is piacciono. You would say Mi piacciono i gatti (literally: "The cats are pleasing to me").