Metaplex is a library that offers ready-made template codes for some purposes to develop Solana programs such as the SPL library. We can say that it is an advanced version of SPL because of the possibilities it offers.

The Solana-powered Metaplex protocol, which consists of two main parts—an on-chain program and a self-hosted front-end web2 application—allows for the creation and minting of non-fungible tokens, auctions, and visualizing NFTs. It offers the opportunity to develop NFT marketplace application with a few lines of code. Since it is open source, you can make additional improvements to the templates and add new features to your program with the Rust language. Unlike SPL, programs are built and deployed using its own CLI’s instead of Solana CLI.

When working with NFTs on the Solana blockchain, one of the most important programs is Token Metadata.

You can find further information about Metadata: https://docs.metaplex.com/programs/token-metadata/overview 

You can create your NFTs in Solana using MetaPlex Candy Machine or using node providers like Moralis. Throughout this part we will be showing you how you can generate NFTs using different sources.

Additional resource for starting a Solana NFT Collection with the Metaplex Candy Machine can be found here: https://www.youtube.com/watch?v=h37srt7Pm_s 

You can find the event records of Solana about Metaplex here:

• Breakpoint 2021: Metaplex and You
• NFT/Metaplex Workshop

Resources:

https://docs.metaplex.com/programs/understanding-programs