1. Scientist - Why does it happen
2. Engineer - How does it work
3. Technologist - What can it be used for
Science is Knowledge and/or understanding about a subject or phenomenon of natural world. Example of Science is Nuclear Physics.
Engineering is application of proven scientific knowledge to create, make or produce something (structures/ product etc.). To use the principles, methods and theories of Nuclear Physics to make a Nuclear Reactor is an example of Engineering.
Technology may be defined as “collection of methods, systems, devices, machines and skills in a procedural way to create complex applications, products etc. Nuclear Power Plant or a Sub-marine may be taken as an example of Technology.