A lawyer is someone who practices law.
An attorney is someone authorized to act for another person -- a person is only an attorney in relation to someone else.
The difference between "lawyer" and "attorney," then, is like the difference between "man" and "husband.." A man can be somebody's husband; a lawyer can be somebody's attorney.
I am a lawyer; if you hire me, I will be your attorney.
Why do some lawyers call themselves "attorneys" or "attorneys and counselors at law" instead of lawyers? For the same reason they tack "Esq." after their names -- they think it sounds more impressive.
Either that, or they are charging by the syllable.
--
Mark.