Positive Discrimination/Action – Favouring a person or group to try to rectify negative treatment in the past

Discrimination is treating a person in a worse way than others because of their sex, race, age or disability.

Positive (in this context) is - favouring a person or group of people.

I'm positive we should actively take this person because of their previous treatment.

So, positive discrimination combines the two meanings above to give: actively giving someone an advantage because they are from a group that has been discriminated against in the past.