Colonizing an area means to settle there. But colonization is also the process of one culture imposing its customs and way of life on another people. This is what happened to the Aboriginal people when the Europeans moved here and colonized America.
Today, Aboriginal people are trying to “decolonize”: they want to regain their independence and their right to make the decisions that affect them. They also want to reverse the negative effects of colonization, for example the loss of parts of their cultures.
They no longer want to be treated as “colonized”, as minorities who are told what to do. But this process is long and difficult because it takes place in a society where there is still a great deal of prejudice.