Lightroom: Question about Clarity

[Christine Aguila]

Hi Everyone:

I have lack-of-clarity about Lightroom's Clarity function.  This is from 
Help:  Clarity:  "Adds depth to an image by increasing local contrast."  I 
don't have an understanding of "local" contrast. What does "local contrast" 
mean?  What is added depth?

Also, I seem to like the photo better when greatly increasing the clarity 
slider.  Fine.  But what's NOT happening in-camera (for example, do I need 
to be making smarter exposure decisions etc) that requires me to add depth 
by way of increased local contrast during processing?

Cheers, Christine