Yup, it’s just what it sounds like. That’s the sun being eclipsed at the same time by both the Earth and the Moon.
This picture was taken by NASA’s Solar Dynamics Observatory and captured by jhon henry osorio orozco. It shows the Earth and the Moon both passing in front of the sun at the exact same time. (And you can view the raw data from that camera, the SDO’s AIA 171 camera, by clicking here.)
How did this conjunction take place? NASA released a fun video: