Paralegal: no J.D. degree; normally has a BS with a paralegal certificate

Senior attorney: someone who has stayed at a firm for more than 5 years (depending on the firm)

Associate: junior level attorney, who stayed at a firm for less than 5 years (depending on the firm)

It takes at least 7 years to become a partner. Some people may not be able to become a partner.  If they stay at the firm, they may be promoted to senior attorney position.

Attorney is just a general name for the lawyer.

If you are really interested in this, check out some firms website.