The ext operator is very similar to the filetype operator. They are so alike that most people simply ignore the difference and use them interchangeably, or drop filetype operator entirely for the ext operator since it is easier to enter on the keyboard.
Originally, the ext operator is a shorthand for the numrange operator. However, it is soon replaced by the newer, further shortened version of the numrange operator: the .. (period period) operator. So eventually (and very naturally), the ext operator became an extension search operator just like the filetype operator.
Use the ext operator for the more uncommon file types because it usually produces a deeper and faster search. The filetype operator on the other hand performs better with common file extensions.
See filetype operator for more information.
