Using the right interaction pattern is a fundamental factor in the success of any activity and the achievement of aims.
Example
The class are doing a dictation activity. The interaction pattern is teacher to the whole group (T-Ss). Other patterns include pair work (S-S), and group work (Ss-Ss).
In the classroom
Different interaction patterns can support the aims of different kinds of activities. For example, if the learners are doing group writing then small Ss-Ss groups are best, but for elicitation of ideas the interaction pattern could be Ss-T. Changing interaction patterns can help vary the pace and choosing an appropriate pattern can help achieve learning aims, for example, making learners take the place of the teacher (S-Ss) can be very productive.
Further links:
https://www.teachingenglish.org.uk/article/working-pairs-groups
https://www.teachingenglish.org.uk/article/how-encourage-manage-active-involvement-group-work
https://www.teachingenglish.org.uk/article/group-work-v-whole-class-activities