When we start reading about radar, we come across various terms which are explained differently. There are various kinds of Radar classified in different ways. This article explains the various radar types in a lucid manner. A Primary Radar transmits high-frequency signals toward the targets. The transmitted pulses are reflected by the target and then received by the same radar. The reflected energy or the echoes are further processed to extract target information. Secondary radar units work with active answer signals. In addition to primary radar, this type of radar uses a transponder on the airborne target/object. The secondary radar unit transmits and also receives high-frequency impulses, the so called interrogation. This isn’t simply reflected, but received by the target by means of a transponder which receives and processes. After this the target answers at another frequency.