Equip only to a Gemini monster. It is treated as an Effect Monster, and gains its effect(s). When this face-up card on the field is sent to the Graveyard, select and Special Summon 1 Normal Monster from your Graveyard.
Equipping it Blazewing Butterfly will allow it to special summon 2 gemini monsters from the graveyard to the field, but only the monster summoned with Blazewing's effect will have the effect available right away.
Equipping it to Phoenix Gearfried can make him into a huge threat. Any time your opponent uses a spell card, you can revive a monster from your graveyard, and any spell/trap card that targets a monster can be negated, and also revive a monster from your graveyard if you use a Supervise.
If your opp destroyed your gemini monster (by battle) using cards like AG Beast, or monster equpped with Baou, which in this case your gemini monster effect in the graveyard is NEGATED, you cant summon these gemini monster from the graveyard due to it still be treated as effect monsters. And supervise can only summon normal monster. I know it's somewhat confusing, but thats the ruling :/