The trigger speed of a trail camera is the amount of time it takes between when motion is detected and when the camera actually takes the picture. It is an interval that can vary greatly from one camera to the next. It is also an aspect of trail cameras that can make a very big difference in the results that are enjoyed.
A trail camera with a fast trigger speed is desirable for when the intended subjects are faster moving animals. Any animal that moves through the field of vision at a reasonable speed is going to be there and gone pretty quickly. A camera with a fast trigger speed is going to frame the animal really well. This, when combined with a large detection zone will give you a greater chance of picking up images that really frame the bucks well.
A camera with a slow trigger speed is more than likely going to miss the animal as it passes through. At best this camera might return a bunch of pictures where you can just make out the animal’s rump as it passes through.
You might use a camera with a slower trigger speed at a place where the animal is likely going to linger for some time. These positions might be at a feeder or a salt block…somewhere the animal is going to be relaxed and slow moving.