Action
Every self has desires, things they would like to be true. To act is to adopt means to attain such a desire, which in relation to these means is the end.
To "adopt" in this sense is not merely to become aware that this action on my part will attain that desire, but to choose this action for that end.
The phrase "rational action" in Classical Economics indicates that the choice of means accords with the self's knowledge. It does not judge whether the end is worthy or the knowledge accurate: a misinformed attempt to attain an unworthy end can still be "rational" in this sense.
Praxeology is the study of action.
The words "praxeology" and "pragmatics" have both been used with various connotations. For my present purposes I prefer the former because I think my theory at this point is close to that of Mises, and indeed owes much to it. However, it seems more convenient to call the associated modality "pragmatic".
"Praxeology is the a priori study of rational (purposeful) action, that is, of the pursuit of ends via means."
Ludwig Mises, Human Action (1949), Part 1.
To choose effectively is to choose suitable means.
If to gain an end I need to develop a skill, undertaking the training to gain that skill is the effective choice in this case; that the skill then grows is a mere fact of zoology, like animal-training.
To identify alternative possible causes of my intended effect (that is, potential alternative means to my end), and to anticipate their side-effects, are epistemic choices, not pragmatic. To act is to choose between the alternatives. The difference between science and engineering reflects this distinction.
Efficiency is one kind of effectiveness. To choose efficiently is to adopt suitable means to optimise some metric.
Economics is the study of efficiency. As such, it is a part of praxeology.
"Economics is essentially a theory of that scope of action in which calculation is applied."
Ludwig Mises, Human Action (1949), Part 2.
A technique is a coherent set of means suited to a certain class of ends.
Technique differs from skill, which is behaviour conditioned by repeated stimuli. Animals have skills but no knowledge of techniques. Some techniques require skill in their application, others not.
The word "technology" properly denotes discourse about technique, but has become attached to the tools which technique produces or uses.
In acting, an agent adjusts particles, cells, organisms, psyches and minds.
Engineering adjusts particles.
Genetic engineering adjusts cells.
Healthcare and Medical Practice aim to adjust organisms to prevent and combat disruptions of the patterns of life (diseases).
Psychotherapy adjusts psyches to support ethoic equilibrium (psychic health, "wellness", often misleadingly called "mental health").
Education adjusts minds. There are moral constraints on this. I hope at some point to elaborate.