What does a constant aperture lens mean?

It is an advantage to ensure that the lens can shoot at a constant large aperture at each focal segment to obtain sufficient shutter speed. Of course, in aperture priority and manual mode, the aperture value can be changed completely. Many such lenses, such as Longteng 17-50, constant maximum aperture 2.8, Canon 50- 1.8, 50- 1.4, are all constant large apertures.