There are so many commands that a comprehensive book about them would be the size of an encyclopedia. This chapter hasn't even covered a tenth of the subject, yet you can do much with what you learned here. If you wish, you may read some manual pages: man 1 sort, man 1 sed, man 1 zip (yes, that's what you think: you can extract or make ZIP archives with GNU/Linux), man 1 convert, and so on. The best way to get accustomed to these tools is to practice and experiment with them, and you will probably find a lot of uses for them, even quite unexpected ones. Have fun! :-)