apt-get install with '-' (minus / hyphen) removes packages

From man apt-get:

install
   install is followed by one or more packages desired for
   installation or upgrading. Each package is a package name, not a
   fully qualified filename (for instance, in a Debian system,
   apt-utils would be the argument provided, not
   apt-utils_1.2.10_amd64.deb). All packages required by the
   package(s) specified for installation will also be retrieved and
   installed. The /etc/apt/sources.list file is used to locate the
   desired packages. If a hyphen is appended to the package name (with
   no intervening space), the identified package will be removed if it
   is installed. Similarly a plus sign can be used to designate a
   package to install. These latter features may be used to override
   decisions made by apt-get's conflict resolution system.