From what I've learned by AIM members (there is a chapter here in Manitoba) is it is a spiritual movement that started in the 70s for spiritual warriors to stand up in protection of the Land and the People being targeted by state violence. They have an official website that could explain who/what they are way better. There are some anti-AIM sentiments out there on the internet but whenever I've seen them take action, it's been at solidarity marches for Missing and Murdered Indigenous Women and Girls to protect marchers from violence.