In great detail, please describe a "Nicotine urge" (smokers only)?

I've been smoking for 6 years. I smoke about 6-12 cigs a day. I think it is a nicotine urge. Just recently, because I've been sick, yesterday I didnt smoke after 2pm. I went to a bar last night for 4 hours and didnt have 1 smoke. That hasnt happened in about 5 years. I woke up today and lasted about 3 hours before I had to have a smoke. I think it was a nicotine urge. I had a strong pull to have a cig. I ALSO believe that its partly mental. Sometimes I might go a few hours and totally forget about smoking, until someone or something reminds me psychologically of it. I believe its a combination of both.