What are the differences between freezing and blocking a card?

Frozen card:

You can freeze and unfreeze your card at any time, for any reason.
While the card is frozen, it cannot be used until you reactivate it.

Blocked card:

This action is permanent.
If you choose to block the card, it will no longer be usable under any circumstances.
If you still have the physical card, you should destroy it.

If any transactions are already being processed at the time of blocking, they will not be affected.