When installing packages

When following tool installation instruction it is common to see this way of doing:

conda install -c defaults -c conda-forge package_name

or

conda install --channel defaults --channel conda-forge package_name

-c and --channel allows to specify one or more channels where conda will fetch the package to be installed.
In this example, conda will search first defaults and then conda-forge if the package is not found in the first.
When you explicitly specify channels with -c and --channel in the conda install command, Conda will use only the channels specified in the command and ignore those defined in your local configuration (the .condarc file).