The "Four in Hand" knot is the most common and great for slim ties and
a narrow collar opening like our JTG shirts.
The "Half Windsor" knot is more of a triangle shape and has an even spread,
can still be tied with a small knot but also works better with a wider collar spread.
Slightly more formal.
The "Full Windsor" is the fatter version of above and works best on wide spread/cutaway collars.