You can use almost any UNIX based book. for a bash introduction you can try:
Now, directly, your problem is in the environment variable PATH.
You show the value being:
The short answer is that it is incorrect.
I don't know where you modified an initialization script (.profile, .bashrc, or maybe /etc/profile).
The PATH environment variable is a list of directory paths to be used to locate a command. Each entry in the list is separated by a ":" character.
Your path has double quotes included, and invalid characters...
There is no path named $PATH.. This likely got included because of the use of single quotes somewhere that blocked the expansion of $PATH to be the existing path list.
There is also no path "/usr/local/bin/apache-maven-2.2.1/bin", as your entry starts with the double quote. That is not a directory name as it is a "special character". It likely got in there the same time as the $PATH portion as otherwise the double quotes might have been taken as meaning quote the value between the double quotes.
As a last ditch workaround (which will go away when you log out/close the terminal window, and is only good for the terminal/terminal window this is done):
In the preceding samples, you were shown to put $PATH in the value of the assignment - don't do that.... In your case it will only include the errors at another level. You MIGHT be able to get around that by putting the $PATH at the end... but that would be because it never tries to use the entries.
This will set the path, and allow most of the commands you expect.
If you have goobered your root login at the same time (and with the same error), then it implies that you modified /etc/profile with the incorrect strings. The easiest way to fix that is to login through a console terminal (alt f2 through f6, one should present a login prompt) login as root, then rename /etc/profile to something like /etc/profile.save. You should now be able to switch back to a GUI and login with a MINIMAL path environment, and use a GUI based editor. You could edit the file immediately if you are familiar with a text/command line based editor (such as vi), and fix the problem immediately.
You can still use the commands you want, even without this - but you have to put the full path to the command.
Where the error is