Which algorithms does the ML agents use?

Maybe, this question was already asked, in this case I'd be very glad if you give me the link.

I'd like to ask about ML agents background. How it works, which algorithms uses.

 

from unity ml agents GitHub:

• Training using two deep reinforcement learning algorithms, Proximal Policy Optimization (PPO) and Soft Actor-Critic (SAC)

https://github.com/Unity-Technologies/ml-agents

 

Thanks