Here is a quick review of terms, if you want to know how each term works in command examples, check CVS mostly used command examples
To request a working copy from the repository. Your working copy reflects the state of the project as of the moment you checked it out; when you and other developers make changes, you must use the commit and update commands to "publish" your changes and view others changes.
To send changes from your working copy into the central repository. Also known as check in.
The situation when two developers try to commit changes to the same region of the same file. CVS notices and points out conflicts, but the developers must resolve them.
A comment you attach to a revision when you commit it, describing the changes. Others can page through the log messages to get a summary of what's been going on in a project.
The master copy where CVS stores a project's full revision history. Each project has exactly one repository.
A committed change in the history of a file or set of files. A revision is one 'snapshot' in a constanly changing project.
To bring other's changes from the repository into your working copy and to show shether your working copy has any uncommitted changes. Be careful not to confuse this with the commit operation; they are complementary, not identical, operations.
Here's a mnemonic to help you remember: update brings your working copy up to date with the repository 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.
Check full command reference in CVS command reference