and ROFL stands for Roll On Floor Laughing
SOF stands for Smile On Face
people use LOL and ROFL even though they may not actually be laughing or rolling on the floor. instead we sit there with a smile on our face because it was a humorous comment but not enough to induce laughter.
dave: yo man i heard a great one today
mord: go for it bro
Dave: why did the chicken cross the road?
Dave: to get to the other side
Dave: what, only an SOF, i LOL'd so hard
mord: sorry bro, it was only SOFworthy