If you need to learn a few useful tools (e.g. sh, kdialog e.t.c.) some of the links on this
page may help.
All you really need to know is the basic commands for copying, moving, removing, and linking files around from the command line (cp, rm, mv, ln). The PBI.*.sh files are just like typing commands into the prompt for the 'sh' shell. Wikpiedia is a good starting point.
Knowing a little about using the shell, wild cards, and quoting (especially * and '') is good and learning simple programing constructs such as 'if elif else' and for loops can save you a lot of typing. When you want or need to do more complex things. But you don't have to learn them in order to make a decent PBI.
A Library is a file that provides additional stuff to an executable that it needs to run but without making for a large exe. So the exe won't run correctly without the libraries but the library makes the exe file smaller. And many programs can use the same 'stuff' in the libraries very effectively that way.
A windows like visuation.
notepad.exe, size 1mb -- requires 'string.dll' to run
wordpad.exe, size 4mb -- requires 'string.dll' to run
string.dll, size 8mb
If the code in string.dll was in both .exe files, they would be a lot larger but wouldn't require string.dll to run. If string.dll is updated all the .exe requiring the file to run benefit from it without being updated themselves. But those that had it 'built in' would not. Thats a nice nutshell explanation imho.