Ores are items or blocks in minecraft, most of the time, you will find Ores underground whilst mining, or sometimes you can aquire them via Villagers
Ores can vairy in rarity
this is what all the ores look like:
Here's the ores in rareity order:
although it says emeralds ar more rare than diamonds, this is true but only when mining, emeralds are very easy to obtain by trading with Villagers and diamonds have more uses
ores have many different uses, you can make armour out of iron, gold and diamonds.
redstone is like the electricity of minecraft, you can make things like automatic farms and doors out of it