The idea of ANN is based on biological neural networks like the brain.
The basis structure of a neural network is the neuron. A neuron in biology consists of three major parts:
The dendrites branch of from the soma in a tree-like way and getting thinner with every branch. They receive signals (impulses) from other neurons at synapses. The axon - there is always only one - also leaves the soma and usually tend to extend for longer distances than the dentrites.