Real newbie question.

Just started fiddling with PostgreSQL, and know nothing of databases.

I have the documentation that came with the Mandrake-8.0 installation
written by Thomas Lockhard, and I've perused Bruce Momjian's book online,
and I cannot find the answer to this problem:

When I am entering values into a table, and make a mistake, sometimes
there is an error message, and sometimes the equal sign in the prompt
becomes a single quote. Error messages I can puzzle out, but I have not
discovered how to recover from the single quote in the prompt. I wind up
having to kill the terminal and start all over

Can someone point me to the explanation of this?

Thanks, and I hope this question isn't too rudimentary for this NG.

Bill Tallman