There are 3 different tiers of ore in Terraria, copper, silver, and gold.
Interesting tidbit on the tiers of ore: Copper is often the first tier of valuable ore found. It has a low amount of health damage associated with it in comparison to silver or gold ores which can hurt for up to 4 hp per strike. The trick is that there’s way more copper than any other kind- not because it’s rarer but because there are more places copper will spawn from then any other metal that comes after copper (silver, platinum etc). Silver can be mined out at area 64 or you might get lucky and find some underground! Gold is both slightly hidden away and also happens to be incredibly happy at producing a better amount of money when you begin your mining. Gold is rare, much more rare than silver but not quite as bad as diamond or platinum when it comes to how difficult it is to find!