Don't be lazy. Read the whole Sounds on Sound series that Mourndark linked for you. Then you wouldn't be asking what an LFO is.
You don't learn to run by just starting to run. You start with a crawl, and then walk, and then run. You used the analogy yourself; I don't know why you'd think it doesn't apply to music.
No one's going to take the time to explain what an LFO is (at least, I really hope they don't) if you won't read an excellent tutorial series that was handed to you. You'll understand the majority of terms you'll see on your Triton from reading those tutorials; the rest, if they're not obvious (for example, I think the Triton uses more than a 4-stage ADSR envelope; if you know what an ADSR envelope is, and spend a minute or two in the Triton manual, the other stages will make sense).
As for oscillators: on a classic synth, you'd just be layering them together - each key would sound both. On the Triton, I'm pretty sure you can map them to different key or velocity ranges. The key range thing probably isn't done that much; velocity ranges are extremely useful. A trumpet sounds different when you're blowing softly than when you're blowing loudly, so you'd want two (or more, if your keyboard or software supports it) oscillators to sound more realistic.
