Well, that's definetly a newbie question
and pretty fundamental ;( In short, "tarbal" is a "tar" archive, most often, compressed with gzip or bzip2 - files with extension ".tar.gz"/".tgz", "tar.bz2" respectivelly. Most of the source code is distributed in such archives. In the Linux world the tarbals are used as extensively as ZIPs in Windows. To install it means to unpack it, compile the source, and place the resulting binaries where they must be. You had probably seen something like this:
$ tar -jxf something.tar.bz2
$ cd something
$ make install
Most Linux distros provide a bunch of already compiled software, usually in ".rpm" (RH based distros) or ".deb" (Debian based) packages, which contain the program files and scripts to place them where they are expected to be. But if there is no precompiled package for the program in question, you must compile it yourself.
As for "Googled a lot ..." - you realy had to gues, that "modprobe" is the command, "loop" is the argument, and to google for "modprobe" only, yet the first results are precizely on the question. BTW, You can get the same info from "man modprobe" in the console window. "man", from "manual", is the standard UNIX help system, you ca get help for "man" itself with "man man". In short, "modprobe" is used for inserting and removing kernel modules. And it's a bit beyond the "newbie" scope.
At the end, i can suggest You to get some good book for beginners, you may look at "tldp.org".