Types of shell variables

There are three types of shell variables available. They are,
a)Local variables
b)Environment variables
c)Shell variables or Special variables

Local variables:
A local variable is a variable, its value will be visible to the current shell.

Environment variables:
An environment variable is a variable, its value will be visible to all the child shell's or child processes started from the shell.

Shell variables or Special variables:
A shell variable or special variable is a variable set by shell for its necessity.Some of these variables are environment variables whereas others are local variables