SLR cameras, or Single-Lens Reflex cameras, are a type of camera that uses a mirror and prism system to allow photographers to see exactly what the lens sees. When you look through the viewfinder, you are looking through the same lens that captures the image, which helps in composing shots accurately. These cameras typically have interchangeable lenses, giving users the flexibility to choose different lenses for various photography styles, such as portrait, landscape, or macro photography. SLR cameras are popular among both amateur and professional photographers for their image quality and control over settings like exposure and focus.