A “string” is just a sequence of letters or symbols. It could be a word, a sentence, a book, a code, a number, or anything. In computing it is important to be able to recognize patterns in strings. For example if your phone receives a signal from the internet, it needs to know whether it is intended for your web browser or your email reader.
An “automaton” is a machine that decides whether a given string has a certain pattern. Thus an automaton is like a very simple computer, and they can be very fun to build. What kinds of patterns can an automaton detect?