Steroids

A steroid is a biologically active organic compound with four rings arranged in a specific molecular configuration. Steroids have two principal biological functions: as important components of cell membranes which alter membrane fluidity; and as signaling molecules. Hundreds of steroids are found in plants, animals, and fungi.
There are many different steroids, testosterone is one type, it increases muscle mass and men produce more of it then women. Other types are progesterone, helps maintain pregnancy among other things. Prednisone, which reduces inflammation to help people with breathing problems.
All testosterone is a steroid, but not every steroid is testosterone.