There are many resources floating around the internet that can help you get started on your NFT. This is a starter pack that contains some of my learnings and take-aways from how I got started. It's an evolving space and it all depends how far you wish to go down the rabbit hole.
How to mint an NFT through Etherscan:
How to Mint an NFT (Part 2/3 of NFT Tutorial Series) | ethereum.org
Punks, Squiggles, and the Future of Generative Media
OpenSea: The Reasonable Revolutionary | The Generalist
What is a Non-Fungible Token (NFT)?
A Non-Fungible-Token is a unique unit/piece of data on a blockchain that is not inter changeable for other items as each NFT has uniquely specific properties. NFTs are largely associate with the Ethereum block chain, however some are built on top of other chains. Due to the decentralised nature of blockchain, the record of ownership of an NFT cannot be tampered with and an NFT can only have one owner at a time.
If you want to explore this concept further you can read this piece "NFT Who, NFT what? What’s this all about?"