Surname First Name Differentiation

Pls can someone give me the differentiation between Surname, first name, and last name? Which one is which because I am trying to fill an important document and it says First name on one gap and Last name on the other gap. Which gap should I put in my surname and my name?
 
In the UK, it is surname before your name.. in US your name before surname
You are partially wrong. In the US, UK, and all the West, their first name comes before their last name (surname). However, in the East (China, Korea, Japan, etc.), their last name (surname) comes before their first name.
 
You are partially wrong. In the US, UK, and all the West, their first name comes before their last name (surname). However, in the East (China, Korea, Japan, etc.), their last name (surname) comes before their first name.
Thanks for the explanation.. where does our middle name come in tho
 
Thanks for the explanation.. where does our middle name come in tho
WESTERN NAME FORMAT
First NameMiddle NameLast Name
DonaldJohnTrump

Although, they don't have middle names in the Eastern world. However, if I was to write Donald John Trump in the Eastern name format, it would go like this:
Last NameFirst NameMiddle Name
TrumpDonaldJohn