Extended writing tasks are text-based assignments that involve:

• research and critical reading from multiple sources of information and ideas, and
• the development of a sustained and well-substantiated argument or point of view.

These tasks are usually set to be undertaken within extended time frames. Students must engage in high-level reasoning and problem-solving as they generate their own creative response to the problem posed. With extended writing tasks, students can engage in deep learning, gain insights into multi-structural connections and relationships among concepts, and develop critical and creative reasoning skills.

-From the UNiversity and New South Wales, https://teaching.unsw.edu.au/assessing-extended-writing