Theater acting — or stage acting — is the first form of the craft. In history, actors had to be prepared to project their voice long distances...or at least to the last row of the audience. This technique is called "projecting to the back of the house." Of course, these days, most actors are mic-ed, so projecting is not much of a problem. In addition, movements of the body had to be larger-than-life so they could be seen by members of the audience. Small movements like a facial expressions are simply too minuscule to "read," so other methods had to be used to express emotion: pacing, dialogue, etc.