All of these are just different ways to say you can cast this for something other than whats printed in the top-right corner. Examples of Alternate Costs Let's look at a few major mechanics that are alternative costs
Commandant has no once-per-turn clause, so a second copy can be activated if the first one is negated (except by Called by the Grave, of course)
Keep your opponent off balance with hand disruption cards like Iono, Judge or the spicy Grabber item card
You can expert merfolk galore, but also some more unusual fantasy races like puffer fish people, penguin people, crab men, walrus women, and something that I would swear was an underwater sliver, if it didn't have the wrong number of limbs
Sure, this adds up, but having 40 life in Commander takes a lot of the sting away
Designator Type Spell Card Archetype D.D