When doing research in an applied field such as speech and language therapy, different sorts of questions are needed depending on what you are trying to understand. As with all attempts at categorisation, the following question types have fuzzy and overlapping boundaries. However, in general, when investigating a particular intervention or practice:

Efficacy questions ask:
Can it work? For whom? How? Why?

Effectiveness questions ask:
Does it actually work? For whom? In what contexts? How? Why?

Implementation questions ask:
Does it get done? By whom? In what contexts? How? Why?

It becomes more complicated to explain what we are doing when we ask efficacy, effectiveness and / or implementation questions about a strategy designed to encourage implementation of an intervention or practice! Nonetheless, attention to implementation is vital.

This will not come as a surprise to speech and language therapists. They have long had to ask all these questions of themselves, their clients and other professionals to try to understand whether and how their intervention strategy may be making a difference. Communication impairment impacts on every aspect of life, and all  strategies (whether they are direct or indirect) depend on work being done.