This article explains how to enable content approval for documents in SharePoint libraries.
Open a SharePoint team site.Create a Document Library.Click on LIBRARY -> Library Settings.On this page click Versioning settings.On this page click Yes to enable content approval.Select create major versions.Under who would see the items.Select only the one to approve the items by default.So now only the approvers will be able to view the document.Click Ok to complete.Now I am uploading the simple document into this library.See the approval status will be pending:Now I am signed in as a different user having read permission the document has been invisible.Now I will approve the document.Review and Approve the document and provide comments.So now see the status has been approved.Now login as a different user.See, the document is now viewble to all the users.
SharePoint Framework (SPFx) A Developers Guide