If you don't know what permalinks are and why they are used you can visit the Wiki page here for an explanation: http://en.wikipedia.org/wiki/Permalink
For our sites, when you first enter a Menu Title, this becomes a permalink for that page (once saved). You can change the Menu Title afterwards, which will change the menu name, but not the URL.
Some would prefer to change the URL, but keep the remaining content intact. Doing so would lose any associated SEO to that URL. There is a way to change the URL and attempt to keep any SEO already in place for that URL.
To do this, perform the following steps:
1) Login to your site as an admin.
2) Go to Pages.
3) Click on the page you want to change the URL for.
4) Click on the HTML icon in the Body's text editor.
5) Copy all the HTML.
6) Go back to Pages.
7) Click Create a new page.
8) Click on the HTML icon in the Body's text editor.
9) Paste the copied HTML into this new page.
10) Put the Menu Title in that you want as your URL. Note: You can change this later if you would rather have the menu tab be different from the URL.
11) Fill in the rest of the information accordingly and Save page.
12) Click on the Gear in the upper-right corner.
13) Click Redirects.
14) Click Add a new redirect.
15) In the Old URL, place the old page's URL. NOTE: You can't put in the full URL, just the tailend.
16) In the New URL, place the new page's URL.
17) Save redirect.
18) Go back to Pages.
19) Click on the old page.
20) Choose to Hide it.
21) Save page.
You should now have the URL you want, with keeping as much SEO as possible. Not all SEO will be kept and more information on why can be found by searching Google. However, since you r new page should have the same information (with the exception of the URL), it should eventually becomes as optimized as the old page.
NOTE: Once a long enough time has passed, you can delete the old page. HOWEVER, if there were images that were uploaded to that page, you will need to upload them to the new page and re-insert them in their respective areas.
The images from the old page are still linked to the new page, so once the old page is gone so are those links.