Rope was one of mans first inventions, even predating the wheel. Rope and knots are two words that go hand in hand, as one would be worthless with out the other. By definition a knot is a method of fastening or securing a length of rope by tying or weaving it.
Knots in history have been associated with primitive religion, folklore, magic, superstitions, to cure evil, even to wave off sickness. Yes, to cure illness or to cause it. Tying knots has numerous of uses. From construction of bridges and houses, to track the passage of time.
A resent study has found that man is not the only specie to tie knots, that gorillas use them to hold creepers and saplings down in their nests. In one nest two dozen knots were counted, most were grannies but some were square knots. There is a bird that ties knots to fasten their nest.
I am sure you are dying to know what the two simplest knots are, and I promises you even you think you can't tie knots you can tie both of these. What do you think they are? If you say the square knot or even the shoe know, your wrong. In my option the simplest knots are the overhand and the larks head.
The overhand knot is one of the most fundamental knots and forms the basis of many other knots. It is how you start tying your shoes, and even how you start the square knot. The overhand knot is not strong, so it is not used in situations where you might expect great force. It also reduces the strength of the rope by about 50%. But as an "anti-slip-knot" it does not have to withstand a lot.
The Larks head, also known as the Cow Hitch & lanyard hitch is often used to loosely attach a rope to a spar or ring. The knot has two redeeming features, it is easy to tie, and it does not jam. The larks head is not overly strong, unless there is tension on both ends of the rope, else it will slip. In reality, this knot is just two single half-hitches.