Longsword is considered to be the traditional Knightly Sword. It's the typical 2 bladed, cross (or simple) hilt which can be used with one or both hands. Your strong hand near the quillions (crossguard) and your weaker one towards the pommel. How spaced you are is a matter of preference but the nearer your back hand is to the pommel, the more fine control you have. It is commonly used in unarmoured combat, and when with armour, it's usually held in half-sword to get the point through the gaps in the armour.
Most systems (not you Vadi, you freak) keep the sword over the back leg.
Often, once you're in closer range you'll take your rear hand off for grapples, locks, disarms and so-on.