Life and World are based on the Networks. All of the creatures and objects are connected together directly or indirectly. Relationship between us is kind of network. To better undrestading and modeling the network, scientists and mathematicians have defined network in high level mathematical term.
Graph helps us to better and more accurate understanding of the relationships we have. In mathematics, and more specifically in graph theory, a graph is a structure amounting to a set of objects in which some pairs of the objects are in some sense "related". The objects correspond to mathematical abstractions called vertices (also called nodes or points) and each of the related pairs of vertices is called an edge (also called an arc or line). Typically, a graph is depicted in diagrammatic form as a set of dots for the vertices, joined by lines or curves for the edges. Graphs are one of the objects of study in discrete mathematics.
Graphs & Networks Graphs and networks are all around us, including technological networks (the internet, power grids, telephone networks, transportation networks, …), social networks (social graphs, affiliation networks, …), information networks (World Wide Web, citation graphs, patent networks, …), biological networks (biochemical networks, neural networks, food webs, …), and many more.