Testosterone blend is basically a mix of injectable sports steroids meant to cover all of your bodybuilding needs. Different laboratories mix and combine various esters and steroids to come up with their custom-made mixes meant to give you a better effect with less side effects:
Test is a number one roid of choice for every bulking bodybuilder. It will not work for cutting though. Every testosterone ester metabolizes into a pure sex hormone indistinguishable from the real one. Thus, the side effects will be way milder.
Blends work best when you have had some prior experience with roids. Since a combination of a few different esters is always more potent giving you a greater energy boost you should know how your body reacts to steroids and how-to time and control your levels properly.
Testosterone does not work for female athletes if they want to avoid any masculinization side effects. Men should also be careful with their cycles as gynecomastia, balding and body acne are still a concern with steroids. Remember to use estrogen blockers and have a course of post cycle therapy once you are done bulking.