BirkenstockUnisex Professional Boston Super Grip Leather Slip Resistant Work Shoe

What does m or n mean in shoe size? Like for example 41 n eu?

Is there a difference in comfort between the super grip and regular boston?

Are these men's or women's size? I need size 41, but they are only showing American size.

Question for seller: when will size 42 (11-11.5/9-9.5) be available? Thank you.