Because with vi there is a potential for data loss or overwriting, you may wish to have a “safe” way to view files. Viewing files with less does just that. The command syntax is

$ less filename

To quit less mode, you can use q, Q, :q, :Q, or ZZ. You can also invoke a search for patterns with /, typing the pattern, and hitting enter. If you accidentally type a slash, you can just backspace until it is gone. Page navigation can be done through the arrow keys, in addition to page up using b (for back) and page down with the space bar. Like with vi, typing Shift+G will bring you to the end of the file.

The man page provides a lot more information on less mode.