What is the workflow of multi-level approval settings in purchasing modules?

When a multi-level approval is configured, whenever the PR/PO/RFQ is created, an approval email is triggered to the configured approval groups at each level. 

On approval by any one of the approvers at level 1, the PR/RFQ/PO approval email is triggered to the next level if configured and so on as it reaches the final level for approval.

Note: While converting a PR into RFQ, it gets auto-approved as PR goes through the approval process.