Leash me to Yak

Big difference between a leash and a line to your yak

 
I'm a new guy here & this is my first post other than my introductory post.

This may be a 'dumb question', but what is the difference between a leash to your kayak & a line to your kayak, or did I miss something?  Thanks.

Leash line is attached to you all the time while a line to your kayak maybe used when needed.