The Physical Layer is the first and lowest layer in the OSI Model. It is the only layer that actually transmits the data from one place to another. It is not concerned with exactly what the data is, rather it is concerned with how to get the bits across wires, cables, or signals.
You can think of the Physical layer as the base of the network. Every other layer depends on it, because without it, nothing can be sent and received. It is similar to the roadways vehicles use; without the roadways, traffic can’t flow.
Among other tasks, one of the Physical Layers functions is transmission of bits. It converts the digital data into signals that can travel across the physical medium. When the signals reach the destination, the signals are converted back into bits. The physical transmission signal can be electrical, light, or radio waves depending on the type of network.
Another important task of the Physical Layer is representation of bits. The Physical Layer determines how the bits will be represented. For example, this can be a high voltage for bit 1 and low voltage as bit 0.
The Physical Layer also defines the topology, or how all devices communicate. It can be a star, bus, ring, or mesh type of structured approach. It also determines It also determines discretion between wired or wireless communication.
