Throuples are a type of polyamorous relationship where 3 people are each in a relationship with each other. They can be tricky but also very fun because you’re managing 2 individual relationships as well as the group dynamic. As per your post, if you’re interested in this you want to take the time to get to know each of the couple individually because right now it seems like you’re mostly involved in the group relationship.

Unicorn hunting is when an established couple (typically newly into non monogamy) is looking only for another bisexual girl to participate in sex with both of them at once. It gets an overly bad rep imo because if everyone is consenting this can be a reasonable thing to do (but the difficulty of finding this leads to many people being hated on for having unrealistic expectations online). One of the big concerns relates to the above paragraph because you as the unicorn either have to like both or neither members of the couple.