Complex sentence: In order for an electrostatic discharge to occur, two preconditions are necessary: firstly, a sufficiently high electric potential between two regions of space must exist, and secondly a high-resistance medium must obstruct the free, unimpeded equalization of the opposite charges.
Split into simpler sentences: In order for an electrostatic discharge to occur, two preconditions are necessary. Firstly, a sufficiently high electric potential between two regions of space must exist and secondly a high-resistance medium must obstruct the free, unimpeded equalization of the opposite charges.