The entire VANET performance depends on the safety and communication messages transferred among the vehicles. Hence, security is most paramount for VANET communication. The trust models compute the trustworthiness of vehicles and enable a secure data transmission between the communicating vehicles. Generally, the trust is estimated in two ways that are direct and indirect. The direct trust model calculates the trust of a node based on the direct communication experience among the entities, whereas the indirect or recommendation trust is computed based on the trust evidence gathered from the trustworthy nodes in the network. Based on communication architecture, the trust models are further categorized into centralized and decentralized. The centralized trust models use a centralized server to establish and maintain the trust of entire VANET nodes, and the decentralized models instruct the distributed trustworthy nodes to compute and maintain the trust values. In the VANET system, most trust models are decentralized to meet the VANET dynamicity.