Linking Objects

Hi CD Community,

I want to know what the purpose of linking an object is.
There are the instructions on how in the Help menu but nothing on why.

I have some bitmaps that blow out the file size and make CD run slowly, so the obvious idea is to reduce document file size, but I thought I read somewhere it makes the file size much larger than embedding. Not sure if true & can't see why.

Also when I go to send the file , say as email attachment, or save to external device, does it collect and embed the object, prior to saving/sending?