What is a 3rd Party and what is its importance for the development of traditional applications?

Although there is a definition in the wikipedia , most of the time this term is co-related to game development. Due to the specific form that the term is treated, the doubt arises whether this concept is applied to the development of traditional software or applications that are not games. I believe that a more general, and less specific elucidation to a branch can help to clarify more people about that term.