Total solar eclipses let us see the Sun's corona, which we can't normally see because of the bright glare from the Sun. But total solar eclipses only happen about once a year and then they only last for a few minutes. That doesn't give us much time to study the corona. A better way is to use special telescopes in space.
Here's a picture taken by SOHO's LASCO telescope. So that we can see the Sun's corona clearly, the Sun itself is hidden behind a black disk which is inside the LASCO instrument. I’ve drawn in a white circle to show where and how big the actual Sun is.