The private key in Wallet Import Format (WIF) as most of us are used to seeing it actually has 3 important parts.
https://en.bitcoin.it/wiki/Wallet_import_format- (1 byte) A version number.
- (32 bytes) The ECDSA private key.
- (4 bytes) A checksum.
By changing the version number, you can generate different bitcoin addresses (one for an uncompressed public key, and the other for a compressed public key) with the same ECDSA private key. This will result in a different WIF (both the version number and the checksum will be affected) for that private key though, so when viewed in the typical format it will appear to be a different private key.
So does that mean everytime I create a new address on the Bitcoin core, a new Priv+Pub pair is generated? If yes, how are they all tied to my own wallet? How does the application keep them together for me?