This question really needs some context to be answered properly, but I will try: "For" generally indicates purpose or giving, example: "This is for cleaning" means you can clean something with this. "This is for you" means I am giving something, and you are receiving it. "To" is a tougher beast. English is strange among languages because it has two word infinitives, and "to" is often a part of an infinitive. "To" can also imply location, giving, or addressing. Examples: "To show" - this is the infinitive of "show" "I'm going to the store" - I am going, and the store is where I am going. "Give this to him" - You are giving, and he will receive this. "I said to him" - I said something, and he heard me. There are plenty of other distinctions, and this is really something that's better with context.