While scientists and engineer have similar training in mathematics and science, scientists have more emphasizes on the theoretical aspects of the world. The primary focus of a scientist is to understand why our world behaves the way it does and their goal is to discover new knowledge. The engineer has a strong background in mathematics and science, but unlike the scientist the engineer puts more emphasize on the practical side of things. An engineer is a people who apply scientific principles to solve problems, and their goal is to create new products.
Engineers are the link between scientific theories and the implementation of technology.
The technician does not have a theoretical background but a practical one. The technician is a person who applies manual skills pertinent to the construction and implementation of a project.