But some of the websites/people explain these two in the wrong way. Mostly the definition for constant would be "A constant is a variable that can't be changed in the program".

{2/9}

It totally makes no sense. This statement states that a CONSTANT is a VARIABLE but it's value can't be changed. If CONSTANT is a VARIABLE then the value can be changed. A total collapse in the meaning.

{3/9}

So, both "Variable" and "Constant" come under a concept called "Identifiers". As the name suggests, identifiers help us to identify a value which is stored in the memory with the help of a name. It's like a box which contains some values/information with a label attached.

{4/9}

Say if you wanna store a number "42" in your program/code, you can assign it to an identifier. So that you can use it later in your program.

{5/9}

If a value stored in an identifier which can be changed in the run time, it is called a "Variable". If it cannot be changed it is called a "Constant".

{6/9}

Values stored in memory can't be accessed without knowing the address. Since we can't remember addresses, we need some kind of label which points to that address. Something like a contact number saved in the phone. We can’t remember phone numbers, but we can remember names.

{8/9}

Also Also identifiers can be function names, type names, class names, labels, etc.,can be function names, type names, class names, labels, etc.,

{9/9}