The phrase "in front of" compares the relative positions of two or more things. For example, you are the first person in a queue and your friend, Timmy, is behind you. There are many others behind Timmy.
You can compare your relative positions by writing: I am in front of everyone else. / I am in front of Timmy. / Timmy and I are in front of the others.
I believe that the next phrase you are asking about is: "at the front of". We can use this phrase to describe the front part of a thing. For example: There is a dent at the front of the car. This is referring to a part of an object.
Of course, you may also wish to write: I am at the front of the queue. In this case, the entire queue is seen as a group. And you are at the front part of the group.
Hope this helps.