A dictogloss is not the same as a dictation, where students try to write down exactly what the teacher reads out.
Example
Learners discuss the sea. The teacher then explains the task, and reads a short text on the sea to the class, who just listen. The teacher reads the text again, and the learners take notes. In groups, the learners then reconstruct the text.
In the classroom
Dictogloss is often regarded as a multiple skills and systems activity. Learners practise listening, writing and speaking (by working in groups) and use vocabulary, grammar and discourse systems in order to complete the task.
Further links:
https://www.teachingenglish.org.uk/article/tattoo-possibilities-higher-level
https://www.teachingenglish.org.uk/article/error-correction-2