In IT world, authorisation is a process of giving the user a permission to enter and use specific resource. It is a step after authentication, when user is identified usually thanks to his username and password. When these match with the data stored in a company’s database, the user is given permission to access specific systems according to his roles and perform certain activities.
An employee wants to access a working group he is assigned to. He provides his username and password. Authentication process proves his identity and he is authorised to get in. He as a user has specific roles, for instance he can add content to this group, but cannot delete other users. If he tries to delete another user, he will not be successful, because he is not authorised to do that.