A Portuguese Opening ( 4 Move checkmate) or call it a scholar's mate

A Portuguese Opening is very important or as you call it a a 4 move checkmate. It's not the quickest checkmate in chess history but it's the 2nd most fastest checkmate in chess. It was created from 1656 text by Francis Beale which adapted the work of the early chess writer : Gioachino Greco. Avoiding the scholars mate is easy but unlike Fool's Mate, which rarely occurs at any level, games ending in Scholar's Mate are quite common among beginners. 

On move 1 go to  Black can play a semi-open defense instead of 1...e5. Openings such as the French Defense (1...e6) or the Scandinavian Defense (1...d5) render Scholar's Mate unviable, while other openings such as the Sicilian Defense (1...c5) make 2.Bc4 a bad move (1.e4 c5 2.Bc4? e6, intending ...d5, gaining time by attacking the c4-bishop and attaining easy equality. Then on move 3 go to 1.e4 e5 2.Qh5 Nc6 3.Bc4, the cleanest way to defend against the mate threat is 3...g6. Should White renew the Qxf7 threat with 4.Qf3, Black can easily defend by 4...Nf6 (see diagram), and develop the f8-bishop later via fianchetto Bg7. Here is a video to show you how to perform a scholar's mate, enjoy !