What is Bit addressability in 8051 or any other microcontroller or processor

Bit addressability means a single bit alone in a register can be accessed. Let us consider the example of 8051 which has the P0, P1, P2, P3 I/O banks.

Here, P0.0,P0.1,P0.2,...P0.7 like that each pin can be accessed. P0 stands for Port and .x(0 to 7) stands for pin number.

Some of the 8051 compiler like keil P0^0 denotes as P0.0.