F is for Forms and Flexibility
Forms a.k.a. Katas are a series of movements performed in a specific order to create a finished sequence. As I mentioned in B the sequence was changed to disguise the actual technique being done and therefore these forms are much more about fluid, graceful movement then they are about fighting. (You have to take them apart and recombine them to see the fighting techniques hidden within.)
Gi-Cho Hyung Il Bu- the very first form we learn. 'Gi-cho' means basic, 'Hyung' means form and 'Il' means One in Chinese, thus the full translation is Basic Form number One.
Forms vary in length (from around 20 or so moves to around 50 or so) and difficulty (upper forms include crane stances, jump kicks and a variety of other difficult techniques) and must be practiced A LOT in order to be performed well. In our school we learn one form per belt level so the higher you progress the more moves there are to remember. Needless to say, it becomes really difficult to remember each and every move when you don't get to practice the form regularly (the mid-level forms all tend to blur together for me, which becomes specifically problematic when I'm trying to teach them move-by-move to green belts '_' ).
Different schools place different emphasis on the importance of forms. Some schools are much more about sparring and spend most of the time and instruction on fighting techniques and practice sparring. Our school's forte is forms- it's what we're known for, what we spend most of our time working on, and subsequently what I myself am best at.
It's been said that the amount of time and training it takes to get insanely good at doing forms is a small fraction of the amount of time and training it takes to get insanely good at fighting. I suck at fighting, so I believe this saying. But I'm sort-of ok with that if it means that my forms can kick-ass.
Flexibility is vitally important for the proper execution of several of our techniques (as many of the comments about the crescent kick post suggest) and therefore stretching is as fundamental to developing one's practice as actually performing the techniques themselves. Subsequently we stretch at the beginning of every class before we warm up and smart practitioners stretch every day at home. While my flexibility is better than some (especially my arms), it's significantly worse than others (because I don't do it at home nearly as much as I should). But like everything, it's only about striving to be the best YOU can be- not comparing yourselves to others and what they can do.
Don't worry, I can't do a full front split, either.