This picture shows glowing loops in the atmosphere of the Sun. The loops are called "coronal loops" be cause they are in the Sun's corona. The corona is part of the Sun's atmosphere. The corona is very, very hot - around a million degrees! The loops are made of glowing plasma, which is like a magnetized gas. Magnetic fields from the Sun form the plasma into curving loops. A satellite named TRACE took this picture in 1999.
Image courtesy TRACE/NASA.