network is a collection of object or entities, that are 
communicate with each other.
mainly network is three type:
1. lan
2.man
3.wan
1. lan stand fo local area network. that limited within the 
office, within the campus 
2.man: stand for metrocity area network that limited with 
the one metro city
3.wan :wide area network

Host : is an entity which can able to provide or render a
particular service(such has Database queries,file transfer),
to store data etc.,

Network : is a medium which connects several hosts. Which
collects the information from a host in a specified format,
carries, routes and hands over the information to he
mentioned host in the same format or in a different format.

physical layer because of dat

Pysical layer is the first OSI layer, it is more related to
the netwok (hardware ) ie cable

Physical layer is the first layer, because it is directly
related with the physical medium of network.

Physical Layer,for any desire communication interconnection 
of the physical component is must..
.Morever it's a foundation for osi