Knowledge types refer to the different categories of understanding and information that individuals can possess. The main types include declarative knowledge, which is factual information about the world, and procedural knowledge, which involves knowing how to perform tasks or skills. Another type is conditional knowledge, which is understanding when and why to use certain information or skills. Additionally, there is tacit knowledge, which is personal and context-specific, often gained through experience and difficult to articulate. In contrast, explicit knowledge is easily communicated and documented, such as in books or databases. Each type plays a crucial role in learning and applying information effectively.