Understanding Abstracts and Papers

Dear Community members,

Can you please tell me the practical use of Call of Abstracts and Call of Papers?
When do we use the call of Papers?

Thank you!

I think this pretty much summarizes the whole worfklow:

A Call for Abstracts is the mechanism through which event organizers invite authors to submit their paper summaries (abstracts). Those abstracts will be reviewed and possibly accepted. The authors of those which are accepted will then be invited (“Call for Papers”) to submit a paper which will be included in the proceedings of the conference. Papers will normally also be peer-reviewed and/or edited.