Replace-By-Fee (RBF) is a node policy that allows an unconfirmed transaction in a mempool to be replaced with a different transaction that spends at least one of the same inputs and which pays a higher transaction fee.| Bitcoin Optech
Covenants are a category of proposed changes to Bitcoin’s consensus rules that would allow a script to prevent an authorized spender from spending to certain other scripts.| Bitcoin Optech
OP_CHECKTEMPLATEVERIFY (CTV) is a proposed new opcode that takes a commitment and requires any transaction executing the opcode to match the commitment in the following fields: its version, locktime, signature scripts, number of inputs, sequences, number of outputs, outputs, and the location of the input being spent within the spending transaction. This allows an output to specify how its funds may be spent—a design known in Bitcoin as a covenant.| Bitcoin Optech