Focusing light into a small spot is vital in many research and industrial fields. In principle, the diffraction nature of light restricts the achievable size of a focal spot referred to as the diffraction limit. Cylindrical vector beams have a promising feature that can surpass this limit in tight focusing conditions. This small focal spot characteristics of vector beams are being extensively applied to optical imaging for spatial resolution enhancement. This study reviews the fundamentals and the recent progress of the small focal spot formation by vector beams. Some advanced features, including superoscillation focusing, dark spot formation, and utilization in laser scanning microscopy, will be discussed in detail herein.