difference between grime and patina

I have acquired paint finished 1920s cabinet that seems to have never been cleaned. From reading the postings I understand that I should remove the grime with mild soap and water. I have tried this and it does remove some of the dirt but the paint is still rather grimy possibly smoke/nicotine stained. I tried a tiny test with a household Mr Clean type liquid and it removed the smoke/nicotine and left the paint rather flat (non-glossy) - have I removed the patina? What should I do to clean this pieic without removing the patina? And if your really patient, perphaps you could tell me what patina really is?