In an attempt to provide easy reference to the CVS terms, we included a short list of the most essential terms.

Repository:
        A repository is a centralized storage area(probably a directory tree) where all the resources of a project is stored. The repository also contains full revision history, so that we can be able to obtain any particular revision of the project. It can also be called as the master copy.

Checking out:
       It means, just obtaining a revision from the repository so that one can be able to modify the source code and thereby enhancing the project or fixing some bugs in it. The checked out copy is called Working Copy.

Checking in or Commiting:
        It is the process of storing the modified source code(from the working copy, where you will make all the changes to your source code) into the repository as a new revision.

Working copy:
        The copy in which you actually make  changes to a project.  There can be many working copies of a given project; generally, each developer has his or her own copy.

A Small Life Cycle:
Discussing a typical scenario would explain the concepts better, instead of throwing some arbitrary terms. Just consider that you want to create a project and put it under version control.

Initially, you will create a directory tree containing all your programs that makeup the project(not necessarily be complete). Then, you want to place all your source files in the Repository. But before that you have to create a repository. This creation process is nothing but Initializing a Repository. The act of placing your initial source code files into the repository is called Import a Project into the repository.

Now, you have set up a repository with a project in it. Then, (obviously) you want to make some changes to your source code so that few bugs can be fixed. Since you are maintaining your source code under version control, you have to request the version control system to get a copy of your source code files. This process is nothing but Checking out a Project(or Module) from the repository.

After few hours or days of work, you have finally broken your head to fix the bugs. But don't relax, now you have one more work left out. You have made changes only to the working copy(or checked out copy) and you haven't stored these changes into the repository. This kind of storing process is called Checking in or Committing changes to the repository. This committing process extends till the wear out phase of your software.