I am a semiconductor specialist. This is difficult to explain, actually I don't understand it well myself, however, let's try.
Did you ever hear about "microchips" or, more properly, "Integrated Circuits"? For example, microprocessors, the heart and brain of the Personal Computer that you are using right now, is an integrated circuit. In the same PC, in your TV set, in your car, in your cellular phone, etc. there are tens or hundreds integrated circuits.
Integrated circuits are used for information processing or for energy conversion. Just for mentioning few of the applications, ICs are used to let an electrical engine working, to turn your car's low-beam on, to set the temperature of ovens, transmit information over long distance, record and play music. Ok, let's stop here, however there is an infinitive quantity of other applications.
So, I am the one who, starting from scratch, makes it possible that a microchip is conceived, defined, implemented, evaluated, released to production, tested and sold.
In my life, I did the same business also with different types of semiconductor, such as power didodes, MOSFETs, IGBTs and some other similar junk, sometimes housed in big electronic modules.
I was emplyed by STMicroelectronics (formerly SGS-Thomson), International Rectifier and Infineon Technologies (formerly Siemens Semiconductor).