I could give you an explanation and a few examples, but you could easily find better ones by checking a few free, online dictionaries. Since you speak Spanish, I’m going to suggest that “to” is usually equivalent to Spanish “a”, and “for” is usually equivalent to Spanish “para” (or “por”, but you’re probably not confusing that one with “to”). Here are a couple of links to get you started: https://en.oxforddictionaries.com/definition/us/for https://en.oxforddictionaries.com/definition/us/to

You use the word "for" in a sentence when stating a reason, a purpose, on some ones behalf, or in favor of. As an example here is a sentence: "I use lotion for my eczema" In the sentence "for" is used to state a purpose. For and to can be used to state reasons or purposes but "to" is used before verbs and for is used before nouns. For example, " I would like to go jogging". In that case to is in front of a verb. If you would like to use the noun form of jog then you would use "for". You would say "I would like to go for a jog". To is also used in relation to people and objects. Such as if you're talking about going to (as an example) the mall then you would say "I'm going to the mall".

I never heard about a language with such complexity about preposition as English (no offense). Take a look: "I've been studying English FOR two years", "I'm looking FOR a house to buy", "I cannot go TO there tonight. I'm too tired" and "I'm going TO Ireland next week". Sadly, there's a bunch of functions that both can assume, I suppose (and I'm not counting with the remains ones [like in, at and so on]). I cannot cover all of them here. And you have to get used to it. But, I recommend to you just Google them (sorry about that, but is the truth). When you'll type to search them, try the "English page" and the "English Grammar online". I'm not a native speaker, and I'm learning them too. However, I hope those tips can help you.