Each Facebook account have a ID number. Facebook ID number can not be changed and it helps differentiate you from others with the same name. Unlike with username, ID number is provided for your Facebook account once created. If someone cannot find you on Facebook (because your name coincides with too many people), you can provide this ID number to help them find you easily by adding immediately after the path http://facebook.com/.
Example: http://facebook.com/100010633215100 :
If your Timeline don't show you Facebook ID, you need do 3 step below.
Step 1, copy your Facebook Username on your Timeline:
Step 2, click here and paste in to blank box:
Step 3, click Find numeric ID :
This is Facebook personal numeric ID: