According to MedlinePlus, a visual acuity measurement of 20/25 is only slightly worse than average. What "20/25" basically means is that a person's eye can see at 25 feet what a typical eye can see at 20 feet.
The standard eye chart used in most optometry offices was invented by the Dutch ophthalmologist Dr. Hermann Snellen in 1862, according to Prevent Blindness. The visual acuity fractions are actually measures of sharpness of sight, meaning that they refer to the eye's ability to pick out small, high-contrast details at a distance. Visual acuity measurements can vary between a person's two eyes.