How do you design an approval process in Salesforce? What are all the configuration components?

An Approval Process routes records for human approval through a defined sequence of steps. Components:
Entry criteria: Formula or filter conditions the record must meet to enter the process. If criteria are not met, the record is rejected (optionally with a message) or another process is tried.
Initial submission actions: Field updates, email alerts, tasks, or outbound messages triggered when the record is first submitted for approval. Records are locked for editing by non-approvers during the process.
Approval steps: Each step defines: (a) filter criteria to determine if this step applies; (b) assigned approver — record owner, queue, related user field, or specific user; (c) approval actions; (d) rejection actions; (e) whether to go back to the previous step or to the final rejection actions on rejection.
Final approval/rejection actions: Actions taken when the process completes (fully approved or finally rejected).
Recall actions: Actions triggered when a submitter recalls a submitted record before approval.
Jump to step: On approval or rejection, you can route back to a specific earlier step for re-review.