user-guide: cache/remote/workspace relationships

[efiop]

Describe how these three relate and what they are.

[shcheklein]

In the user guide the part about basic DVC concepts is missing. Like described in #144 the User Guide should be starting with some introduction to those concepts with some explanation and how they relate to each other. This introduction should server as a reference when we use these concepts in other documents (e.g. command references, and/or examples, tutorials).

Basic concepts should include:

• working space
• cache
• remote
• dvc file
• etc

[jorgeorpinel]

• We should probably also clarify that DVC remotes are not very much like Git remotes. They are cache backups and not distributed copies of the entire DVC repo. Per Default push behaviour not analogous to git. #1087 (comment)

[jorgeorpinel]

Guys, can we close this old one in favor of #550 (comment) ? I feel like the community is mostly aware of these differences/relationships now but adding the concepts section will help too.

[shcheklein]

Yes, we can close (the title of #550 is misleading to my mind - it was never about (only) SEO, it about introducing people into concepts and their relationships - like this ticket)