Your question is about Jovians only, and Xspuipuke gives the general rule exactly right. The practical implication: this applies to all other tag types as well. When you play on Tharsis, for example, the wild tag does not count towards the number of Science tags you have when the Scientist award is scored at game end - because you are not taking an action at that point. But when you want to play AI Central and have only 2 "genuine" science tags in play, the wild tag will count as a science tag, the third one in this case, you meet the AI Central qualifying condition that you have three science tags, and you can play AI Central as an action. Same story for counting the number of any tags when you play a card (Jovian tag count when playing TG, plant tag count when playing Insects or NRA, earth tag count for playing Cartel, Builder tag count for playing Medical lab, and so on), or claim a milestone (playing a card is an action, and so is claiming a milestone).
The only features of the wild tag that remain slightly odd to me, even though people can offer explanations for this: when you play Point Luna, playing any card/prelude with a wild tag doesn't trigger the Point Luna effect of giving an extra card. And you don't get a discount on Research Coordination if your corporation gives discounts on tags (Valley Trust on Science tags, CSM on Building tags, etc).
[edit: the logic: the wild tag can only be used when it is already in play. See BGG discussion with the designer clarifying all the above - https://boardgamegeek.com/thread/203085 ... ion/page/1. The more exact conditions given by Jacob Fryxelius:
The wild tag can only be chosen
- by the owning player
- during the owner's action
- if it is already in play
At all other times the wild tag counts as no tag at all (and can thus actually trigger Community Services).
and:
As a consequence of these rules, it can be used for: * milestones, * tag requirements, * Cards that count tags.
I got curious and recalled seeing this discussion earlier, so dug it up again.]
