Answer - A variable is like a name. It is defined as a character string to which a value is assigned, where values could be the number, text, filename, etc. The shell maintains the set of internal variables as well as enables deletion, assignment, and the creation of variables. Thus, a shell variable is a special variable that is set by the shell and is required by the shell in order to function correctly. Some of these variables are environment variables whereas others are local variables. So, the shell variables are a combination of identifiers and assigned values that exist within the shell. These variables are local to the shell in which they are defined as well as they work in a particular way. They may have default value or values can be assigned manually by using appropriate assignment command. To define a shell variable, the set command is used. To delete a shell variable, the unset command is used.