What are Dim, Modifier and Sub ( ) vs Private Sub ( )?

Hi,

I know above are the things explailed all over the web and one does not need much google to find these.

But nobody has explained these things for a layman who is new to programing world.

I have made some good macros but still I don't know what are following things;

1- What the _ell is the dim word? What if it were never born?

2- Why do we call them modifiers?

3- Why some people prefer to write Private Sub Name() instead of simply writing Sub Name()

Please explain above things to a layman.

(I am not a lay man)