New noob with many questions

[atreyu]

do I understand it correctly that a Linux ap from Ubuntu may not work under Linux OS from Fedora?

yes, but only b/c the package was compiled against a set of libraries that are known to be installed on a given distro. You may liken it to a Windows app that is compiled for Windows XP that does not run on Windows 7. There are cases where you'll find an app that is generic enough, or statically built so that the Linux version will run on most any Linux platform (like the Linux firefox binary that Mozilla provides, for example).

And if there is an Ubuntu package that you want for Fedora, for example, it is very likely you'll find it in Fedora's repos (and vice versa).

[benbob1]

First step in the learning process taken, by the sound of it.
This brings up the next question: which version has the richest choice in aps?

[jayd512]

This brings up the next question: which version has the richest choice in aps?

I would have to say Debian and its' derivatives. Debian has something to the tune of 35000 pre-compiled software choices available in their repositories.

[benbob1]

...Debian has something to the tune of 35000 pre-compiled software choices available in their repositories.

That will do for starters.

[atreyu]

IDebian has something to the tune of 35000 pre-compiled software choices available in their repositories.

For a rough comparison, I have Fedora 17 with the ATrpms and RPMfusion repos enabled, along with the regular Fedora/Update repos, that puts the total around 26,000.

[MASONTX]

Short answer, maybe. Kind of like a windows 8 ap may or may not run on an XP install. Each distro tweaks aps to run on their distro, and puts them in the repositories for their distro. There are ways to do this tweaking yourself if you want an ap your repository doesn't have, but I have never done this myself. For my needs, I find that either an Ubuntu based or debian based distro will have all the aps I use, and there are so many debian and ubuntu based distro's, that it is no problem to find a distro I like.

[hazel]

The app itself will work, once installed, but the packaging may be wrong. Different distros have different ways of packaging apps and a RedHat package can't be installed in Debian or vice versa. In addition, the app may have been built against different versions of basic libraries than the ones you have on your machine; that's why you should never try to install software from repositories that belong to other distributions. However, if you really need some particular program and it isn't in your distro's repository, you can always download source code and build it locally.

[benbob1]

... if you really need some particular program and it isn't in your distro's repository, you can always download source code and build it locally.

You seem to have more confidence in my coding abilities than I do myself.

[jayd512]

You seem to have more confidence in my coding abilities than I do myself.

Nonsense! Compiling from source may seem daunting at first, but it's not really all that difficult... no coding experience needed.
I should know... I can barely write a usable bash script, but I can compile from source.
Take a look here.

[atreyu]

You seem to have more confidence in my coding abilities than I do myself.

not coding, compiling. compiling is much simpler than coding b/c the compiler does most of the work (though it is still hard to trouble-shoot when it doesn't work). you can often install a package from source with these generic steps:

# first get the package
wget http://website/foo-1.23.tar.gz

# uncompress it
tar zxf foo-1.23.tar.gz

# cd into the dir created by extracting the tarball
cd foo-1.23

# now configure/make/install the package
./configure
make
sudo make install

Edit: Jay has set you right w/his link