three kinds of electrical systems:
direct current
directly substitutes for a battery
single alternating current
easy to change the voltage so you can transmit longer distances with less loss
split is a way of using a single current to try to get some of the advantages of polyphase
polyphase alternating current (two or more, out of phase)
much more efficient motors but no better than single alternating for lighting

first level understanding of the technology:

What do we learn in these chapters about Tesla's process of invention:

Tesla gets the opportunity to work for the Edison company in Paris
but they aren't yet interested in motors or AC

he got a chance to experiment with actually building an AC motor in Strasbourg in late 1883
discovered that what he imagined in his mind didn't initially work because there were other issues such as using the right materials

Tesla is beginning to look unsuccessfully for a partner to put up money to develop the motor

Tesla's success in improving dynamos (generators) gets him a job with the Edison company in New York (the city does not impress him)

Quits because he doesn't get bonuses and the arc lighting system he designs isn't put into use, finds partners to build an arc lighting system in New Jersey but they then drop the manufacturing side and leave Tesla with no profits from his inventions

Tesla then invented a very simple thermoelectric motor
This brought him partners who better understood new technology
and business strategy--an alternative set up patents made it possible to set up a competing company
they even supported Tesla as he tried generating ideas that did not work

Patent and business strategy at the time:

Tesla turned back to the motor and figured out how to do it with two polyphase currents (four wires) instead of 3, but wasn't interested in the simpler split phase (two wire)

meanwhile alternating current is catching on, led by Westinghouse, but it isn't the right kind of alternating current