The ERC-777 is a token standard that is tradable and derived out of ERC-20 tokens. The ERC-777 offers new ways to engage with the token contract while keeping backward compatibility.
The ERC-777 is used to facilitate any complicated token trade interaction. Using a unique feature known as a hook, ERC-777 tokens can remove the ambiguity around minting, burning, and decimals.
Although the earlier version of the ERC-777 standard was plagued with some serious security issues, it has been resolved since then. Although it still retains some drawbacks, which is why the updated ERC-820 token standard was introduced offering the same functionality.