There are two main types of electrical circuits: series circuits and parallel circuits. In a series circuit, the components are connected end to end so there is only one path for current to flow. If one component fails, the entire circuit is broken. In a parallel circuit, the components are connected side by side so there are multiple paths for current to flow. If one component fails, the others can still function. Series circuits have higher total resistance and the same current flowing through all components. Parallel circuits have lower total resistance and current can vary between paths.