Question

What seperates the second and third generation computers?

Answer 1

Second generation computers were based on transistors, essentially the same as first generation computers, but with the transistors replacing the vacuum tubes / thermionic valves.

Third generation computers used printed circuit boards to replace much of the wiring between the transistors. This had the advantage that components could be mass produced, reducing the number of errors because of incorrect wiring and making the component boards replacable.