While we go around the Sun once a year, until now, we’ve only been able to see one side of the Sun at any given time. That was before the STEREO probes were in place— one on one side of our star and one on the other, giving us stereoscopic vision of our Sun. Being able to see both sides at once gives us valuable insight on solar storms, flares and how has, heat and energy moves around.
Events that happen anywhere on the Sun can have a ripple effect everywhere else… literally. A solar flare is a vast explosion on the Sun’s surface, releasing as much energy in a few minutes as millions or even billions of nuclear bombs. This sends gigantic seismic waves, ripples, across the Sun’s surface, affecting other regions. Gigantic coronal mass ejections (CMEs) are like hurricanes over the Sun, and the region causing one can extend onto the far side of the Sun where we can’t see it. Solar prominences and other features can be huge, stretching across the face of the Sun, again hiding part from view.
And, of course, in astronomy more is better. Having a better view, a better vantage point, just plain ol’ more data, is a big help.