We interact with many people on daily basis. Some are of our group and some are from different group. When we are interacting in our own group the words like "we" and "us" are used and every problem, situation, emotion are actually felt.

When we are interacting with people outside our group it becomes quite formal and it is related with some specific goal or purpose.

For example - If I am talking with the students of my class who belong to my group, it will be a very friendly, very informal talk and we can easily understand emotions as well as the feelings behind everything said. Whereas when we are talking to the students of some other class it will be quite a formal talk and will include only the general subjects which are of common interest or it will be regarding sharing some information or asking for some help.