Blaze rods are obtained by killing blazes, which spawn in Nether fortresses. They are a renewable resource.
Blazes drop 0–1 Blaze Rod when killed by a player. The maximum is increased by 1 per level of Looting, for a maximum of 0–4 with Looting III.
Blaze rods are primarily used to craft blaze powder, which is required for brewing potions and crafting Eyes of Ender. They are also used to craft brewing stands, making them necessary for potion brewing and accessing the End dimension.