OSI Stands for open system interconnection model. This is reference or virtual model, you cannot see it , touch it ,but its exists conceptually just like electron, protons etc.
OSI model is invented by ISO(International standard organization). ISO is non profit organization that defines several standards. It is just like other standard e.g ISI mark, IEEE, CE etc that you must have come across.These standard work for the welfare of society for setting different standard in different areas like food , electronic networks etc.
OSI model have seven layer describe as below.
1)Physical layer
2)Data link layer
3)Network layer
4)Transport layer
5)Session layer
6)Presentation layer
7)Application layer
