Can someone explain what actions this command will perform?
sudo apt-get install xyz
Indeed, lets break this down.
So, as a whole, this command attempts to find and install package/program xyz on your machine and does so as root if you are able to authenticate as such.
Note: "apt-get install" will also install missing dependencies for the xyz package.
for future reference, the man command can help with commands
just type
man *yourCommand*
or in your case
man sudo
man apt-get
This is more of a ServerFault.com question than StackOverflow, but it instructs the package manager to install the xyz program.
sudo - do this as an administrative user apt-get - the package management program install - the instruction for the program xyz - the program to install
In order to see the repository that would be used to install a package, use the following:
apt-get --print-uris install xyz
then answer "Y". The URIs will be printed, but the package won't be installed.
To see what repositories you have configured, look at this file /etc/apt/sources.list
which can be edited (but you should probably use System>Administration>Software Sources
to choose repositories.
To see what versions of a package are available to be installed, and from what repository, try
apt-cache policy xyz