No, it has nothing to do with receiving fees. It is not a wallet and has nothing to do with your wallet balance.
When you make a transaction you have to pay a transaction fee. The question is, what fee should you pay? To deal with that, Bitcoin Core has a feerate estimator which looks at transactions in the mempool and how long it takes for those transactions to confirm. It then produces an estimate for various confirmation time targets. These estimates are stored in the fee_estimates.dat file.
