Transactions confirm by miners because miners do the math and solve blocks. You can run a full nodes without ASICs which are used by miners to mine Bitcoin blocks and confirm transactions.
To Run a full node you need to download the whole blockchain which is at current 494 GB on your system as you don't have to depend on others for getting data if you need any and can retrieve it directly and validate the transaction.So you need to have this much memory at current with more as size is increasing day by day so need extra disk space if you are running full node client.