It can be compared with intensive reading, which means reading in detail with specific learning aims and tasks.
Example
A teacher reads a short story with learners, but does not set them any tasks except to read and listen.
In the classroom
Extensive reading is often overlooked, especially as a classroom activity. Teachers often feel it is not an effective use of class time or are just uncomfortable with the extended silence. Learners can be encouraged to read extensively by setting up a class library, encouraging review writing, and incorporating reading of books into the syllabus, and dedicating some class time to quiet reading.
Further links:
https://www.teachingenglish.org.uk/article/extensive-reading
https://www.teachingenglish.org.uk/article/extensive-reading-why-it-good-our-students%E2%80%A6-us
https://www.teachingenglish.org.uk/article/using-texts-constructively-what-are-texts
I consider one can set aside time to read, however, the big question is: Are all students ready to spend half-an-hour in silence, just reading as his/her classmates? what can we do with those students who have special needs in terms of education? can they be so quite reading?