Alienation is the feeling of being left out, not belonging or not understanding yourself in relation to your environment. Alienation can be talked about in many ways. In psychology, researchers talk about alienation in terms of how well or unwell people fit in to their social groups. This may include how well people relate to their peers in a school or workplace, and how connected they feel to those around them.
In sociology, alienation is a more complex and difficult idea. Alienation is how people understand themselves in relation to their entire society. A good example of this is how people think of themselves when they are working and doing a job. Karl Marx wrote about this. This kind of alienation happens when people do work that they are not interested in or find boring. However, in almost all societies some people may have to do jobs that they don't like because they need to earn money. This can be seen as a type of alienation because a person's true feelings and their actions are separated and unrelated. On the other hand, a person might feel empowered and connected if they do a job that they do like. Empowerment and the feeling of being connected is the opposite of alienation.
Alienation is also a key element in the existentialism of Sartre and Camus. The connection between these ideas is the theme of Colin Wilson's The Outsider (1956). Anomie is another related idea.