[Canada?] Sport and Comfort mode
 

Is it safe to switch between the two while the car is in motion?

Yep, no problems on my end. I do it quite frequently.

what differences between comfort and sport mod?

It shouldn't be a problem, but the manual says to only change the program when the transmission is in park. When in C, the car starts more gently in either direction except full throttle starts. It also improves traction and stability on icy roads and upshifts occur earlier so that there is reduced wheel spin. I usually leave it in S for dry conditions and C for wet and snowy conditions.

Sport is more responsive on the throttle. You'll start in 1st gear from a dead stop as opposed to 2nd in comfort most of the time. The rpm's will stay in the power band for a longer period of time delivering a more consistent flow of power.

It's more of a European feature when driving through the mountains. When you put your foot on the gas it finds the gear and you get around pretty zippy. If you've driven in mountainous terrains you'll know what it means. On the majority of North American roads, I don't find the feature makes little difference. Since you're already using an auto transmission you want the tranny to do the work for you. If you feel the urge to take control just shift the gears yourself.

It's a nice to have, psychologically it makes you feel better - come on admit it, I will! I feel the car instantly becomes more powerful and responsive when I press the CS button lol.