Anvils allow you to enchant anything, but the /enchant command doesn't

You can't /enchant something that can't normally be enchanted in survival mode, like putting Knockback on an axe, which is kind of silly to not allow being that it is a weapon, but you can use an anvil to put Knockback on anything, including literally a grass block, without even using cheats.

Steps to reproduce

1. Get a netherite axe and hold it
2. run /enchant @s knockback 2

the command fails

3. Get a Knockback II enchanted book

Try to combine the book with the axe.

Notice The anvil allows it (and that the enchantment functions as it would with any other tool).