In this tutorial, you use the NetBeans IDE to create a simple, graphical, REST-based client that displays Twitter public timeline messages and lets you view and update your Twitter status. The application uses Swing and NetBeans IDE's support for Twitter's SaaS operations.
Simply put, a 'runlevel' determines which programs are executed at system startup. Most of your exposure to run levels will deal with system startup. You will become intimately familiar with the exceptions the first time you have to troubleshoot a failed system.
Make is one of the original Unix tools for Software Engineering. By S.I. Feldman of AT&T Bell Labs circa 1975. But there are public domain versions (eg. GNU) and versions for other systems (eg. Vax/VMS).
Related tools are the language compilers (cc, f77, lex, yacc, etc.) and shell programming tools (eg. awk, sed, cp, rm, etc.). You need to know how to use these.
Important adjuncts are lint (source code checking for obvious errors) ctags (locate functions, etc. in source code) and mkdepend. These are nice, and good programmers use them.
Important, and related tools, are the software revision systems SCCS (Source Code Control System) and RCS (Revision Control System — the recommended choice)
The idea is to automate and optimize the construction of programs/files — ie. to leave enough foot prints so that others can follow.