Bitcoin core is a software where you download the entire Bitcoin software and you become a validator node of the network, the software downloads all the transactions in the history of Bitcoin and it takes up a lot of space in your HDD to tell the truth, but it has an option of wallet and you can receive bitcoin and send it between peers, it is one of the safest wallets, it was created by Satoshi Nakamoto himself, but this crypto wallet may be for slightly more advanced users, but it is really safe to store your bitcoins, the seed phrase is in a file called wallet.dat where to make a backup you will only have to copy this file and paste it into your new bitcoin core for example on another computer