usability of AF mode on dslr camera nikon and canon

1. AF-S or single point focus (Nikon) or One Shot (Canon)
   
   This mode is a very easy mode to understand, because this mode is intended for static or immovable subject like landscape photography, still life, model etc., just by pressing the shutter button half and then the camera will lock the focus point, and jebret! (J), if the subject is suddenly moving, but the focus point will not change. What to remember when using this mode, the subject must be "true or not moving, because the slightest movement will make the focus becomes inaccurate again and the image becomes less sharp or blur
2. AF-C or Continuous auto focus (Nikon) or AI Servo (Canon)
   
   Another One Shot is also AI Servo, if this is the opposite of One Shot, this mode is used for dynamic or moving subjects, the way it works when autofocus is selected and the mode set in AI Servo when we press half the shutter button then the focus point will follow the movement subject, subject motion will then be predicted by the camera and the focus point will change following the direction of the subject motion, you as the user only need to press half the shutter button and follow where the subject of the subject, when the sense of the subject is in the right position and then jebret !. Auto focus mode AI Servo is suitable for use in sport photography, wildlife photography, and some areas of photography with moving subjects.
3. AF-A (Nikon) or AI-Focus (Canon)
   
   The last mode is AI-Focus which is a combination of One Shot and AI Servo mode, the way it works is automation, when the subject moves to be motionless or silent will resemble a one shot performance, when the subject is stationary and suddenly moving it will work like an AI mode Servo, this mode is commonly used for subjects whose motion is uncertain, can suddenly move or still, like photographing a dancing person. For beginners this mode is the safest mode, which does not need to quickly change the mode, but the weakness of this mode works automatically according to the camera command, automation on the camera has a possibility of wrong in determining the focus.

study the difference each.
hopefully.