Recipes
Recipes are a way to define a way to craft a particular item. They are defined by a plugin or datapack, however we are only going to cover the plugin side of things here.
A shaped recipe is a recipe that requires a specific pattern of items in the crafting grid to craft an item. These are created using a pattern string and a map of characters to items. The pattern strings are 3, 3-character strings that represent the rows of the crafting grid. They can be created as follows:
public class TestPlugin extends JavaPlugin {
    @Override    public void onEnable() {        NamespacedKey key = new NamespacedKey(this, "television");
        ItemStack item = ItemStack.of(Material.BLACK_WOOL);        item.setData(DataComponentTypes.ITEM_NAME, Component.text("Television"));
        ShapedRecipe recipe = new ShapedRecipe(key, item);        recipe.shape("AAA", "ABA", "AAA");        recipe.setIngredient('A', Material.WHITE_CONCRETE);        recipe.setIngredient('B', Material.BLACK_STAINED_GLASS_PANE);
        getServer().addRecipe(recipe);    }}This recipe would require a television to be crafted with one black stained glass pane surrounded by white concrete. The result would look like this in the crafting grid:
AAAABAAAAA shapeless recipe is a recipe that requires a specific number of items in the crafting grid to craft an item. These are created using a list of items. They can be created as follows:
public class TestPlugin extends JavaPlugin {
    @Override    public void onEnable() {        NamespacedKey key = new NamespacedKey(this, "WarriorSword");        ItemStack item = ItemStack.of(Material.DIAMOND_SWORD);
        ShapelessRecipe recipe = new ShapelessRecipe(key, item);        recipe.addIngredient(3, Material.DIAMOND);        recipe.addIngredient(2, Material.STICK);
        getServer().addRecipe(recipe);    }}This recipe declares that you simply need 3 diamonds and 2 sticks to craft the item, without any specific orientation of the cross pattern in the crafting grid. This could be crafted in any of the following ways:
  DSS   |   SDS   |   S D  D     |   D     |   D  D     |   D     |   D SAnd, any other composition of the 5 items.