If the bypass ratio is greater than 4:1 then the engine is referred to as a high bypass turbofan.
   
Page 3-7*                                                                                                                                Page 3-7 *

Turbofan engines often have 3 stages

Page 3-19 *

High bypass engines are very efficient at subsonic speed but don't work for supersonic aircraft.

http://www.boeing.com/companyoffices/gallery/images/commercial/747400er-02.html

Turbofans can be quite large and powerful. The 747-400 can be equipped with four P&W 4062 that deliver 63,300 lbs (281.57 kN) of thrust and have a bypass ratio of 4.8:1 to 5:1  (www.Boeing.com)
 
 

Page 3-9 *
                 This is not a 747 engine but it is almost the same size

*Whenever there is a page number underneath a diagram the picture is from
A&P Technician Powerplant Textbook published by Jeppesen Sanderson Inc., 1997