To is a preposition. Also, It is used as part of the infinitive. Let me explain the use of **to a little. 1) We can use to as a preposition to indicate a destination or direction: Example: We are going to London. To in the example was used to indicate the destination. You can also use to for direction. 2) We use to with verbs such as give, send, write, to indicate the person or thing that receives or experiences the object of the verb: Example: I gave the letters to my mother. 3) We use to before a verb to make the to infinitive form: Example: I need to wake up early tomorrow. Use of For 1) We use for to talk about a purpose or a reason for something: Example : I am going for a lunch. 2) We frequently use for to introduce the person or people receiving something: Example : I bought a pen for my father. 3) We use for with a period of time to refer to duration: Example : There is an amazing beach. I usually go there for a couple of hours at the weekend