Direct instruction (DI) is a learning strategy where the material being learned is communicated directly from the explainer to the learner, potentially with additional work by the learner to explore and absorb it with guidance from the explainer.
In the classroom setting
We talk of direct instruction most often in the context of a synchronous explainer and learner, for instance, in a classroom.
A classroom with direct instruction will include a lecture component (with the explainer doing the bulk of the talking, communicating the material to the learner). This lecture component may be punctuated by interactive activities such as cold calling, polling, and in-class desk work. There may also be other activities outside the classroom, such as homework assignments and quizzes.
In asynchronous settings
Educational materials, such as textbooks, that are consistent with direct instruction will usually explicitly articulate the material they intend to convey, and then include exercises or other questions.