Different type of knots include:

Overhand knot
Used to make a knob on a rope, or as the commencement of another knot.

Figure of Eight
Used as a stop knot, turned in the end of a sheet. Does not jam like the overhand

Reef knot
A common and well known knot used for joining two ropes of equal diameter. Will slip under strain applied to the two standing parts

Thief Knot (Fools Knot)
Will slip under the slightest strain. Traditionally used to detect unauthorised entry to a sailors kit bag

Bowline
A useful and common knot which forms a loop that can not slip

Running Bowline
Makes a temporary running noose

Bowline on a bight
Used to make a a pair of fixed-size loops in a line. Can be used to make an emergency bow swain’s chair

Fisherman's knot
Used for joining two ropes of unequal diameters. Will not slip under strain

Surgeons Knot
Used in tying a ligature around a cut artery

Wall Knot
Knot worked in the end of a rope