Engineers solve problems. They create. They invent, design, build, operate....... Tools, Machines, Systems, Structures. The two classes of engineers are categorized based on the two types of problems that we have.
The 1st set of problems that we face has to do with constraints on our resources. This could be time, money, space. Engineers come up with solutions that help us use these resources more productively. Hence the tools that they construct may help us save time, space or money. Calculators save us time. Skyscrapers save us space. Google saves us time, space and money.
The 2nd group of engineers solves the issue of what to do with all the extra resources that the 1st set has freed up for us. They create smartphone apps.