What is the difference between absolute and relative Xpath?

Absolute Xpath : 

1) start selection from the document node
2) Starts with //
3) e.g. “/html/body/p” matches all the paragraph elements

Google Search Box : /html/body/div[1]/div[2]/div[1]/div[1]/div[3]/div/div/div/form/fieldset[2]/div/div/div

Relative Xpath  : 

1) start selection matching anywhere in the document
2) Starts with /
3) e.g. “//p” matches all the paragraph elements starts with p

Google Search Box : //*[@id='gbqfqwb']