Card says: Action: Cancel and discard target unit or support card just played unless its controller spends all resources in his pool.

What does "just played" actually mean?

does it mean:

Just Played the card from my hand to the play area

or

used an ability or action of a card that was already in the play area

or both above options?

Been looking for clarification to no avail.

Thanks in advance for the help.

Got the answer from the FAQ!

In summary, to play a card means to play it from your hand paying the cost.