A solar eclipse happens two or more times a year. Some are partial, some where the sun is bigger or surrounds the moon (annular), and total, where the moon covers the whole sun and only the corona is visible. The last total solar eclipse visible in the US was 1979, and the next is 2024, but not nearly the same amount of viewable locations as 2017.
The diamond-ring effect happens at the beginning and end of totality, where the diamond (or gem in the gem state) appears for a second or two. The uneven surface of the moon lets the light shine around the moon, which creates an effect like glittering diamonds called Baily's Beads.
Additional info from NASA: https://eclipse2017.nasa.gov/sites/default/files/publications/Eclipse2017presskit.pdf