Hi! Very cool that you’re writing about Cosmos. To be clear there is the Cosmos Network (many different blockchains that will soon be connected together) and there is the Cosmos Hub (ATOM), the most well-known chain in the Cosmos Network. I assume you’re asking about the Hub.
When you say reserve pool, I’m guessing you mean the Community Pool. In short it’s an account where a portion (currently 2%) of all staking rewards and transaction fees are diverted. They accumulate here and are then disbursed via a governance proposal. You can read more about this here: https://github.com/gavinly/CosmosCommunitySpend
I don’t recall what happens when ATOMs are burned eg. in a slashing event. @ebuchman or @sunnya97or @zaki @zaki_iqlusion will almost definitely know.