what is the term describing the process in which users delegate a certain amount of over to the chain to participate in blockchain network maintenance through validation?

The term you’re looking for is “staking delegation” (often just called “delegation” in a proof‑of‑stake context). In many proof‑of‑stake and delegated proof‑of‑stake blockchains, users delegate their stake (tokens / voting power) to validators who actually run the nodes and perform validation and network maintenance, while the users share in the rewards and help secure the chain without operating infrastructure themselves.