Slug

What exactly should I put when entering in the “slug”

“The “slug” is the URL-friendly version of the name. It is usually all lowercase and contains only letters, numbers, and hyphens.”

My site is https://www.BackpackersGuideToThailand.com

(appreicated if you have a look to understand better).
I have the page set up as I want Now I want to start writing.

When creating a new category from

(https://backpackersguidetothailand.com/wp-admin/edit-tags.php?taxonomy=category)

and begin posting for example under the heading “about us”

What do I put in that box called Slug?

Do I simply put “aboutus” or the full “https://backpackersguidetothailand.com/aboutus”

Thanks in advance