Approvals is a native Teams application that lets you create, manage, and share approval requests and sign-offs. You can quickly start an approval flow from the same place you send a chat, have a channel conversation, or from the approvals app itself.

When using Approvals, you just need to select an approval type, add details, attach files, and choose approvers. Once submitted, approvers are notified and can review and act on the request. The app also allows you to require that responses are completed in an assigned order (sequential approvals), if you choose.

For more information, see Microsoft's video training for Approvals.

You can also review Microsoft Learn documentation for how to 

• Set up Approvals 
• Create an approval from a chat or channel 
• Respond to an approval request