apt-mark is nothing like masking from gentoo. A-M is just for making modifications to the database that remembers whether a package was intentionally installed or was automatically pulled in as part of a dependency. This database is how apt generates the list of "packages that were automatically installed and no longer needed." The closest thing that I can think of to masking in Debi an is pulling in a package from experimental or a PPA that you added. There are no packages in the repo (stable, testing, unstable) you are using that require anything other than "apt-get install package" to install them.
A-M is the recommended way to hold a package, previously you would use `dpkg --get-selections`. All apt/dpkg commands will abide by what you set with A-M.