Angels are one of the two supernaturals, representing the heavenly realm. If it wasn't already obvious, God is their patron.
Angel appearances range in all ages, however most are between 10 and 25 in looks. That appeared age becomes their technical age on Earth. They have large, white, feathery wings, but other than that their physical characteristics are just as diverse as humans. Some not-as-human eye colors can include lavender and bright colors, however on Earth their eyes ARE NORMAL HUMAN COLORS most of the time, excluding when they use their powers.
Speaking of powers, angelic powers have a large range, from simple healing to firey destruction. However, there is no darkness behind them, only light. Any elemental affinities are usually Water, Grass/Plant, Air, Fire, Light (anything else you MUST ASK first, and check the Demon elements to make sure it isn't on that list.) There are some cross overs with Demonic elements, however the way they control them differs, eg gold or red fire as opposed to blue or black fire. Remember, in the human realm powers are severly limited from normal, so no amazing giant attacks that wipe out whole cities, or raising the dead.
When angels fall in love with humans: It doesn't require any "making love". Once the angel and human start to feel something for each other (MUST BE MUTUAL), the human starts experiencing strange effects, like cleansing water unwillingly, fast healing, and enhanced physical abilities. However, should they kiss, the human becomes fully in control of these powers, and often are completely altered by them, not always in a good way. They are what use to be called "Fallen Angels". They have the ability to spurt black wings, heal others, and sometimes even more powerful than angels in the element they aquire (these elements are unlimited. Can be demonic.) Because of such a huge gain in power, it's not uncommon for humans to forget completely about their angelic lover and instead turn to their power. Most of the time, however, angel-lovers remain good.
If you have questions, feel free to drop a comment. I will add it to the post if it's good.