An engineer is a professional in the field of technology. The term is French and ultimately comes from the Latin word "ingenium". It means something like "ingeniously invented tool". In the past, engineers were the ones who built siege weapons for war.
Today we are surrounded by many technical devices, and almost everywhere the work of engineers has been incorporated. Engineers develop, design, calculate and improve technical equipment, bridges, buildings or machines. To do this, they have to be well versed in natural sciences such as physics, chemistry or biology, including mathematics.
If you want to become an engineer, you usually study at a university or university of applied sciences. But you can also do an apprenticeship first and then go on to study. The certificate for engineers used to be called a "diploma", which is why people speak of a "Diplom-Ingenieur". Today, the degrees are called Bachelor's and Master's.