This document discusses the memristor, which is described as the fourth basic circuit element along with the resistor, capacitor, and inductor. It provides details on what a memristor is, why it is called a memristor, how it works, its appearance and invention, types of memristors, applications, advantages, disadvantages, and its potential role in replacing transistors and as logic gate circuits. The key points are that a memristor is a passive and non-linear two-terminal element whose resistance depends on the amount and direction of charge that has previously flowed through it, allowing it to remember the last resistance.