definition: the reason why people take a particular action
If something is done on a particular basis, it is done according to that method, system, or principle.
If you say that you are acting on the basis of something, you are giving that as the reason for your action.
Some movies have been banned on the basis that they are too violent.
She was chosen for the job on the basis of her qualifications.
她因资历适合而获选中担任这项工作。