Several types of knots can be distinguished for a variety of purposes. Although in many cases any knot can be used for any specific purpose, these specialised knots have been invented to be able to perform any specific job in the most efficient way (e.g. facilitating untying after a job has been done).
This is a simplified list of knots which keeps a balance between usage for many purposes, reasonably good performance (e.g. easy untying, difficulty of laying the knot) and a fair amount of simplification (to avoid needing to learn a great number of them). These basic knots will still allow you to help yourself out in survival situations and in low-tech construction (e.g. in the developing world).
Figure-eight knot for making a part of a rope too big to fit back through a hole
Lark's head for vertically (gravitational tensing) hanging, or horizontally (if tension is assured) link a rope to another or to an object if slippage can be avoided by that object structure, position and or stability.
Reef knot a specialization of theLark's head for tying two lines or the ends of a single line together such that they will secure something that is unlikely to move much, initial tension will make it more reliable than the simplerLark's head if constant tension is not guaranteed.
A knot tied with a hitch around one of its parts, contrasted. with a loop, which is closed with a bend. A slip knot can be closed, a loop remains the same size(slip knots).
