This is a big subject, requiring whole books to answer. Start by looking for basic electricity courses online. When you have learned enough to ask specific questions about concepts you have difficulty with, members here will be happy to answer them.
You could start with classics, like Tanenbaum books Computer Networks or Modern Operating Systems, old books but very interesting. you might as well enroll in basic computer and networking courses.
You can find hundreds of them for free. You could start with the simpler ones, and if you want, you can move on to the more complex ones.
