The title of this picture is Six Rainbows Across Norway. I'll just shut up for a second while you admire the awesomeness.
Done? Ok, here's how it happened:
Rainbow #1, the primary rainbow, was created the old fashioned way by sunlight reflected off the backs of raindrops. If you're saying to yourself, "which side of the raindrop is the back?!" then we're on the same page. Turns out that just means the side opposite where the light entered the drop; like if I ran into your house, bounced off a wall, and ran back out the front. Except I doubt I'd come out prettier than I went in. The reason that works for rainbows is that white sunlight is actually light of various colors blending to appear white. The different colors of light reflect at different angles, causing them to fan out inside the raindrop. When they exit, the separate bands of color are visible to the human eye. Rainbow!
Rainbow #2, the secondary rainbow, is created when the light ricochets around inside the raindrop a little more than usual. Imagine I ran into your house again, but this time I bounced off all the walls and part of me flew out the window and part of me went out the door. Ok, maybe that's a bad analogy, but you get what I mean. Because the secondary rainbow is basically a reflection of a reflection, the colors are inversed from those of the primary rainbow.
Rainbow #3 is a reflected rainbow, and this is where it gets weird. A reflected rainbow appears when light hits the raindrops, comes out all rainbowed-up, then reflects off a body of water and finally is projected in the sky. This extra reflection causes the rainbow to show up at a strange angle, which is determined by the sun's altitude. Reflected rainbows should not be confused with reflection rainbows, although I imagine they often are. Reflection rainbows occur when light hits the body of water first, then the raindrops. They wind up having the same end points as the primary rainbow, but a much larger arc.
The other three of the six rainbows are just the first three reflected in the water's surface, which you likely figured out for yourself. I'm sure a rainbow purist would argue that there are only three actual rainbows in the picture, but I don't know any rainbow purists and if I did they'd probably be jerks.
Extra bonus fact-- Since I just used every variant of the word 'reflect' more times than I ever thought possible, I figured I'd look the thing up. It comes from the Latin reflectere, meaning 'to bend back'. Fascinating. More interesting is that 'reflectedly' is a real word. I dare you to use that in a sentence that doesn't sound incredibly awkward. Double dog dare you.