Skill level and your opponents.
Skill level: You might see a professional open JTs UTG at a 9 handed table. But that's because they are more skilled, and can therefore turn more mediocre hands into profit even when they have bad positional advantage.
Oh, and that's also one: Position. You should aim to play around 4 times as many hands from the button than from EP. In EP you should have a very tight range.
So as a beginner, look up a holdem opening hands chart and stick to that in the beginning.
Your opponents: You should always look at what types of opponents you have at the table. If a nit opens, then you have to tighten your range, and if a very loose agressive player opens, you can loosen up your range a bit. Also important to look at the opponents that are left to act. Especially against good aggressive players in the blinds, you should be more selective about the hands you choose to steal with from the CO or Button.