This animation from NASA shows the path of totality that can be expected for the NATIONAL ECLIPSE on August 21, 2017. To experience the total phase of the eclipse, you must be located within the narrow center shadow. Areas outside the path of totality will get a partial solar eclipse only.
During a total solar eclipse, anyone located within the narrow center shadow of the Moon, called the umbra, experiences the total phase of the eclipse, or "totality." Within the much wider outer shadow, the penumbra, the Sun is only partially obscured.
A solar eclipse can only occur during a new Moon, the phase of the Moon when it's positioned directly between the Earth and the Sun. Because the Moon's orbit around the Earth is tilted, not every new Moon results in an eclipse. This NASA animation shows how everything will line up just right on August 21, 2017.
In the most accurate visualization of an eclipse path to date, NASA's Goddard Space Flight Center shows that the Moon's shadow isn't a smooth oval, but a polygon with a jagged, irregular edge. This is caused both by the peaks and valleys along the lunar limb as well as the topography along the path of totality on Earth.
The last total solar eclipse before the NATIONAL ECLIPSE occurred on March 8/9, 2016, when parts of Indonesia and the Federated States of Micronesia were plunged into darkness. People in Hawaii and most parts of Alaska saw a partial solar eclipse. This NASA animation shows the path of totality.
On September 27, 2015, millions witnessed a supermoon lunar eclipse when the Moon passed into the Earth's shadow during its closest orbital approach. This animation from NASA's Goddard Space Flight Center explains what a supermoon is, how a lunar eclipse occurs, and how rare this combination really is.