In silico Modeling is otherwise known as computer modeling. It allows you to simulate behaviors on a computer screen. “Researchers have developed a wide range of sophisticated computer models that simulate human biology and the progression of developing diseases” (“Alternatives to Animal Testing”). Using computers will allow researchers to visualize and predict what the human response will be to a specific drug or substance.
Another part of computer modeling is QSAR or Quantitative Structure- Activity Relationships. The Journal of Molecular Structure: THEOCHEM explains that “the basis for any structure–activity relationship is that the biological activity of a new or untested chemical can be inferred from the molecular structure, or properties, of similar compounds whose activities have already been assessed” (Schultz, 2003). The journal also states that this relationship with more of a general-rule and gives “yes or no or at best, ranking information” (Schultz, 2003). Basically quantitative structure- activity relationships give a likelihood of something being bad or dangerous based on previous  results of other, similar substances and the basic knowledge of how are bodies work.