Sessions is a very nice feature provided by vim. Using sessions, you can store the current working status of Vim (files, tabs, positions, etc.) in a file and reload it upon opening the next time. This is quite similar to workspaces provided by other Text Editors and IDEs.
To save the current working in to a session:
:mksession /path/to/file
or in short,
:mks /path/to/session/file
To load the session upon opening next time,
$ vim -S /path/to/session/file
directly from shell or
:source /path/to/session/file
from inside Vim.