Activity

Activity is a “teaching/learning unity”, in which the participants are active and not spectators.”

It seems to me that inquiry in mathematics, as a mode of activity for pupils learning mathematics, has processes in common with both inquiry in developing mathematics teaching and inquiry in the research process. […] Investigation was a mode of learning, a way of designing activity for pupils and a way of developing teaching. Thus I see inquiry in three mutually embedded forms or layers: 
Inquiry in mathematics: Pupils in schools learning mathematics through exploration in tasks and problems in classrooms; 
Inquiry in teaching mathematics: teachers using inquiry to explore the design and implementation of tasks, problems and activity in classrooms;
– Inquiry in research which results in developing the teaching of mathematics […]”

References:

Jaworski, B. (2004). Grappling with complexity: Co-learning in inquiry communities in mathematics teaching development. Proceedings of the 28th PME Conference. Bergen, Norway: Bergen University College.