A decidable language is a type of formal language for which there exists an algorithm that can determine whether any given string belongs to that language. This means that for every possible input, the algorithm will eventually provide a yes or no answer, indicating membership in the language. In the context of theory of computation, decidable languages are often associated with Turing machines, which are abstract machines used to model computation. If a language is decidable, it implies that there is a systematic way to solve problems related to that language, making it easier to analyze and understand.