In SharePoint you can choose whether a document has to be checked out before you can edit it, or you can edit a document without checking it out.

When you check out a document, a checked out icon appears next to the document icon. This means nobody can make changes to the document except the person who did the checkout.

You can change the behavior by going to the document library settings, below General Settings choose  “Versioning Settings”. Change the last option on the next page (Require check out) to Yes or No.