A tag is a keyword or label that categorizes your question with other, similar questions. Using the right tags makes it easier for others to find and answer your question.
For questions regarding .eth, the Ethereum Top Level Domain.
Mostly BIP39, an open standard for encoding a seed as a series of common words, but also collects other methodologies.
for questions related to interacting with or developing for Ethereum and Ethereum-compatible blockchains using sbt-ethereum.
an instruction on the EVM that returns the size of the data of the last function call.