TOPIC: Page title

When editing a page, a  required page title field is the first field.  Right below is an optional page title field.  It says: "Optionally specify a different title to appear in the <title> tag of the page."  I can't see any changes regardless what I enter.  What is this for?
Thanks.

Is one the title that runs across the top of the page and the other what appears in the nav bar? Not sure.

Winner, Winner, Chicken Dinner Oh and a karma point

Thanks Dom. I do remember some of the things you taught me. The others I have to go back and find my old threads.

But but but...on my "contact me" page, I have "Contact Me" in the first field and "Contact me for a Home Inspection" in the second field.  "Contact me for a Home Inspection" doesn't show up anyplace where I can find it.  I thought the name in the navigation bar is from the URL path.

It's that darn theme 26. It's the only theme that I didn't make and downloaded (it was nice and flexible). Looks like it handles the title tag differently. I'll have to check it out when I have some time. What Ian stated is how it should be working.