Here are the meanings of the two prepositons "to and for" that you asked about: For 1. Duration of time: We walked for two hours. 2. Distance: I walked for five kilometers. 3. Purpose: I bought this jacket for you / We should meet for lunch 4. In the direction of: She left for New York. (to go to New York) 5. In favor of: We are for the proposal. We are cheering for the Chinese team. 6. Considering: The boy is clever for his age. (considering how young the boy is) 'for us' would be definition 3 - the important thing is important because it will benefit us to know - it is good for us to know. To 1. In the direction of: Turn to the right. 2. Destination: I am going to Beijing. 3. Until: from Monday to Friday / five minutes to ten 4. Compared with: They prefer basketball to football 5. With indirect object: Please give it to me. 6. As part of infinitive: I like to ski / he wants to help. 7. In order to do something: We went to the store to buy soap. 'to us' would be definition 5 - 'us' is the indirect object - the important thing is something that we must know, therefore, it is important for us to know. Some examples: It is important for us to get the information as soon as possible, so we can make a good decision. It is good for us (we benefit) to exercise every day. The information is important to us (for us to have) so we need it as soon as possible. If we exercise every day, our bodies will be good to us (our bodies will be healthier and stronger). Receiving 1,000,000 yuan will be good for us. I wish someone would give a 1,000,000 yuan to me. I hope my answer is helpful to you. I hope I have explained this well for you.