The official guide asks for a formal text suited to a given context, written from graphic or written input. One option gives a chart, infographic or diagram and asks for an academic text, a report or an article. The other gives a short text, such as an advert, a news item, a review, part of an opinion article or a letter to a newspaper, and asks for a formal letter or email such as a complaint, a request or a recommendation. The task tests whether you can produce a formal text that fits a specific context.
The same four categories as in task 1 apply, with fit and task fulfilment (Adecuación y cumplimiento de la Tarea 2) in place of mediation, and the two tasks count equally. In band 2 for that category, the text answers the points but misreads or only partly answers one, or leaves out some relevant content, and shows some inconsistency that takes away from its naturalness.
The lesson on writing task 2 explains how to choose between the options and works through a report. The official model exam for this task is listed on the C1 model exams page.