Let's start with some basic concepts, Machine learning as a general concept, is fairly simple and is similar to how humans learn. Machines teach themselves based on patterns that they "see" in data or images, giving them the ability to program themselves. The efficiency of machine learning is measured primarily in the variables of precision and recall. The easiest way to think of precision is with the AI you probably interact with most frequently: a search engine. Let's say that you do a Google search for "purple polka dotted cat bed" and that gets you 50 results, and of those results, only 25 are actually relevant (ie. 25 of those web pages have purple polka dotted cat beds).