Most of my friends are interested in martial arts, even my female friends. Whether it be shotokan, PRIDE fighting, judo, or even bread and butter stuff like boxing or shooting - they love sports that approximate battle. So when fencing comes up, they want to know - does modern Olympic fencing have anything to do with fighting someone with a sharp sword?
It's a simple question with a complex answer. The question, as short as it is - really asks a couple questions. The first is how well does modern fencing approximate dueling with sharp weapons. The second is how well does fencing prepare you for an actual sword fight. The third is are the weapons in fencing suitable for actual fighting (if they were sharp).
Let's start with the last question, since it is the easiest to answer. The modern foil, whose design is determined by the Federation Internationale D'Escrime (FIE), is no more a real weapon than a similar sized piece of rebar. The blade is rectangular, allowing no edges, and its flex refuses to send any amount of force into its target - making it ideal as a safe weapon for beginners as well as competition. Only when the blade is broken does it become anywhere near life threatening - but in that state the techniques used to wield the weapon become useless. (Although I know one demented fencer who keeps a sharpened foil near his bedside for protection.)
The sabre, with a grip that facilitates the cut, is similar to the foil. Again, its flex and square cross-section makes it useless as an actual weapon - unless the blade breaks. And then it is QUITE dangerous.
The competition epee, however, was always designed to accurately approximate a real dueling sword. Aldo Nadi, a world champion fencer, famously dueled with his competition epee sans pointe d'arret. The weapon's heft is strong enough to leave deep bruises even when the opponent is properly attired in a fencing uniform, and many styles of blade have only enough flex to prevent accidental breakage - but no more. So it seems out of the three key weapons in Olympic fencing, only the epee would be suitable for combat if sharp.
The next question in increasing difficulty is whether or not the movements in Olympic fencing resemble a real swordfight. Only those who fence AND remember the days of fighting with yardsticks when the teacher was away from the classroom know the answer... and it is absolutely yes. While an observer might simply see two people hacking at each others blades - a combatant has a clear intention of parrying an impending attack - whether that attack come by fencing sabre, sharp broadsword, or yardstick. An advanced technique that was developed by broadswordsmen and still used by fencers and schoolboys everywhere is the feint and the second intention attack. A second intention attack simply means I am going to convince you I am attacking in one line (or area of your body) or feint , draw your parry to that line, and then attack another newly undefended line. While in modern fencing this strategy may or may not always work - it was highly effective when fighting in suits of armour. The combined weight of the sword and the armour insured that a missed parry or counter attack sealed your doom. Here the second intention attack is quite deadly. So yes, most techniques you learn in fencing today would directly apply to most types of actual swordfighting.
Now that we know that an epee but not a foil or sabre is useful in a real fight, and the techniques in fencing are applicable to sharp weapons - now we can answer if fencing would prepare you to handle yourself in a real fight. The answer is not necessarily. For a sport that is designed around time honored techniques used to kill people, it is very safe. Materials with the same properties as kevlar are used in the uniforms - and the tips are flat and round to the point that successful fencers rarely cause their opponents any pain. Due to the rules in fencing - getting hit is also not necessarily a bad thing. In foil and sabre, if you are hit off target or you hit off target before your opponent touches you - there is no point scored. In epee, a double touch means both sides get a point - and if you are winning, then simply attempting double touches until the bout ends is a reasonable strategy. As Aldo Nadi noted, thinking like this in an actual fight is going to get you killed. As someone who fences and has been in a knife fight (many years ago thankfully), the mindset is completely different between the two - and one doesn't prepare you for the other. While the techniques are similar - sport is not war.
So is fencing "real?" In most ways that count, yes it is.