ls: Lists the content of the current directory.

 ls -a: List all files including hidden files.

 ls -l: Use long listing format (displays permissions, owner, size, date, etc...).

 ls | less: Pipe the directory listing into less for easy viewing.

 cd path: Change to the directory specified by path.

 cd ~ : change to your home directory.

 cd - : change to your previous directory.

 cd .. : change to the current directory's parent.

 cp source_path destination_path: Copy files from source to destination.

 cp -R source_path destination_path: Recursive copy.

 mkdir directory: Make a new directory.
 mv source_path destination_path: Move or rename files.
 rm files: Remove files.
 rm -R directory: Recursive delete.
 rmdir directory: Remove an empty directory.
 touch file: Create an empty file.

 find path -name filename: Find the file called filename starting the search from path.
 locate filename Find files in the database whose names contain filename.

 cat filename: Print the contents of a text file called filename to the screen.
 grep string filename: Search for and display lines of filename that contain occurrences of string.
 less filename: Scroll through the content of a text file. Press q to quit.
 pico filename: Open filename in a simple text editor.
 sort filename: Sort the lines in filename by alphabetical order.

 bunzip2 filename.bz2: Uncompress a bzip2 file (*.bz2). Used for big files.
 gunzip filename.gz: Uncompress a gzipped (.gz) archive.
 unzip filename.zip: Uncompress a PkZip or WinZip file (*.zip)
 tar -xvf filename.tar: Untar a tar (.tar) archive (tarball).
 tar -xvzf filename.tar.gz: Uncompress and untar a compressed tar archive (*.tar.gz or *.tgz).