An image in a mirror is formed by reflecting light.
Reflection is the bouncing of light off of a reflective surface, such as a mirror.
An image in a reflection is formed by light bouncing off of a surface.
What causes an image to reflect?

[a] the sun
[b] fibers
[c] erosion
[d] a wave
[e] Light
[f] heat
[g] photons
[h] forces