Chapter 3 expands on the essential definition of “task” presented towards the end of Chapter 2. The chapter presents a range of theoretical definitions of task, alongside several examples of tasks, with a view to developing a more comprehensive understanding of this central construct for the purposes of TBLT. It starts from the premise that the construct of task has been subject to a range of definitions over the years. However, a somewhat more consolidated position began to emerge in the late 1990s and 2000s. The essential characteristics of a task for the purposes of TBLT can be identified as: (1) a relationship to real-world activities (a dimension of authenticity); (2) a focus on communicative meaning and fluency (rather than grammatical form and accuracy); (3) a gap (something that learners have to find out); (4) an outcome beyond the use of language (language is not used as an end in itself). The chapter concludes by presenting a range of task types that reflect these definitions.