HR = Hunter Rank
If you press start and look at your status, you'll see you're probably HR1.
Do the quests in the guild hall, the first few stars are HR1, complete all of them and you get an urgent quest, a blangonga I think (might be wrong), and after you do that you'll be HR2.
The higher the monster's level, up to HR9, the harder it is, and the better equipment you require. High rank monsters also have some different attacks from low rank ones.