1. What species of tree is this?
This is a red alder (Alnus rubra). Note the bright color of the inner bark that gives it its scientific name.
2. What happened to it?
The damage to the bark is typical of an ungulate rub. Because of the height on the tree (which is a little difficult to ascertain in this picture) I believe it was from an Elk (Cervus elaphus).
3. Approximately how old is the damage?
The damage was fairly recent. As the wound on the tree ages the color will dull significantly, also note the fresh bark that has fallen on top of the vegetation on the ground. There are several leaves on top of the fallen bark which suggests it probably hadn't occurred within the past few hours but it had definitely occurred that fall. I have not studied the relevant clues enough (e.g. how quickly the color dulls in the bark) to feel comfortable being too much more specific than that. But take a look at Dancingfrog's interesting analysis in the comments.
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