Meaning of #define

What does this really mean?

I understand why #include is needed, but i don’t understand what is meant by #define. Could anyone help explain it to me in alternative ways?

#define is used here in a variable sense, the variable is being set to a given value.

Wouldn’t that be the purpose of #include ? I’m kinda confused between #include and #define.

No, that is inserting the contents of a file. Nothing directly to do with a variable at all.

ah i see! got a better sense of it now. thanks a lot!