Totality is when the moon blocks all the light from the sun, and even then the Path of totality is a stripe 50- 100 miles wide -- as you get further from the path of totality you then see a partial eclipse -meaning the sun is not totally blocked.
I am located roughly 200 miles from the path of totality, and even in that small distance I am only 91% Total

The easiest way to understand the big picture here is to remember that the earth's orbit around the sun is an ellipse (not a circle) and the Moon's orbit around the earth is also an ellipse.
So for a total eclipse to occur the moon has to be close enough to the earth to block the whole sun, but even then the darkest part of the moon's shadow (the Umbra) is only about 50- 100 miles wide (depending on how far the moon is from the earth at the time of the eclipse). If you move outside of that you start to see a bit of the sun thus for YOU the eclipse is partial. And a sliver of the sun can cause the same damage as the whole sun.
I hope this helps