Mirrorless cameras and DSLR cameras both offer interchangeable lenses and advanced features, but they differ primarily in their internal mechanisms. DSLR cameras use a mirror and optical viewfinder system, while mirrorless cameras employ an electronic viewfinder or rely solely on the rear LCD screen for composing images. Mirrorless cameras tend to be more compact and lightweight, while DSLRs often offer larger battery capacity and a wider range of lens options.