Help me understand more about cryto.

So I just recently started to learn more about other coins than eth and maybe start exploring the function of crypto that I can use.

What I’m confused about is why these services need their own coin. One dapp I found called Aave (it seems pretty well know) has its own coin for example. Why exactly is that needed for their own services and how exactly does using Aave effect the price of the Aave coin?

Just in my limited experience with the dapp it look like you don’t need it. I can lend out my eth for another coin or do anything like that with a bunch of coins but the Aave coin isn’t necessary.

I’m just confused on what the point of the Aave coin is and why one would buy it.

This would go for any other Dapp that has its own coin too. How is the price of the coin related to the usage of the Dapp?