Has anyone used Aave lending platform?

[SiverSurfer]

Hi guys, I've recently deposited some stablecoins to Aave in hope of earning some interest (done with the ups and downs on DeFi pools)

I have two questions
1) What's the difference between Aave 1 and Aave 2 market
2) I see that there's an option for my savings to "Can be used as collateral". My intuition says no without doing my due diligence, hence a quick wonder if anyone knows this.

thank