why do we see loops?

Here is a TRACE movie showing a spectacular arcade of loops during a solar flare.

Sometimes only one or two loops appear together. However, this false-colour image shows a multi-loop group in an active region at the limb. The blue shows plasma at 1,300,000 °C, green shows plasma at 1,600,000 °C and red shows plasma at 2,000,000 °C.