Approvals
Approvals are an optional second set of eyes: named people who approve a configuration change before it goes ahead.
Approvals are entirely optional. Turn them on when a change deserves a look before it becomes part of your configuration; leave them off when you'd rather move quickly. They show up in two places, and both work the same friendly way.
Named approvers and how many
When you set up an approval, you choose the approvers: specific people, or groups of people, who can approve. You also choose how many of them need to say yes: any one of them, everyone, or a set number. That way a small change might need one person while a bigger one needs several.
Not your own change
Under Who can approve in Settings there's a checkbox, Someone other than the person who made the change. It's on to start with, so whoever proposes a change set doesn't approve it themselves.
The number of approvals needed comes down to match. Say you named three approvers and asked for two of them. If one of those three wrote the change set, it needs two approvals from the other two. Turn the checkbox off if you're a team of one and you'd rather approve your own work.
Approving a change set
A workspace can ask that every change set be approved before it becomes part of your configuration. The change set waits, in the open, until enough approvers say yes. Nothing is written down until then.
Approving at a pipeline stage
A pipeline stage can carry a checkpoint that asks for approval before a change is applied to that environment. Same idea, at delivery time: the change pauses at the stage and waits until someone approves it.
