I think we've all seen an A-line skirt before, but we've never really been able to identify them by name. If you don't shop regularly or haven't made sewing a part of your career, being able to list skirt features on sight probably isn't a skill you have.
But A-line skirts can easily be identified by looking like, well, and A. With a sort of cinched waist and a bottom that flares out, they skirt the line of semi formal fairly easily. Looking profession in one just takes a pair of flats or heels paired with anything besides a t-shirt.
If you've always wanted a pampered sort of look but don't have pampered time, and A-line skirt is perfect for you. It gives the allusion of having a tailored piece and looks fairly expensive if you iron in correctly. It's probably the best way of showing off your legs, second only to bodycon / skin tight skirts.
Like most pieces, it's easier to get the high quality look if you avoid mixing too many patterns. Going one tone is a great place for beginners to start, and if you pick something with a silky inner lining, it can feel really nice.