What is For ?
For is (prep) 1. showing the purpose or use of something This plastic bag is for the apples. What’s that key for? what did she say that for? why did she say that? for example, for instance to mention one thing among many Some animals, for example polar bears, are not used to hot weather. 2. showing why something is given What did you get for your birthday? What shall we buy her for Christmas? 3. showing the person who receives something There was no mail for you this morning. I’m making a cup of tea for my mother. 4. showing how long something happens He has gone to France for two days. We’ve been waiting here for hours. 5. showing distance You can see for miles from the top of the hill. The motorway goes for kilometres without any service stations. 6. showing where someone or something is going Is this the plane for Edinburgh? When is the next bus for Oxford Circus? 7. in exchange for something She gave me £10 for the silver spoon. That old computer is no use I wouldn’t give you anything for it. 8. in support of; in order to get We’re striking for higher pay. 9. in the place of someone Can you write this letter for me? 10. with the purpose of to go for a walk He was running for the bus. All these items are for sale.
source: Easier English, Student Dictionary Upper Intermediate Level