They don't.
How do gems understand the concept on love?
Anthony Morgan
Michael Moore
In terms of the species what is the benefit of fusion feeling good? I understand that’s it a way for weaker gems to become stronger but I don’t don’t the benefit in it feeling good
Landon Cooper
The fusion feels only as good as the actual relationship between the gems in question is. If the fusion feels good, that means the components will be more likely to stay together, meaning the fusion will be strong and stable. A stable fusion will less likely get unfused due to internal and external factors.
Kayden Hall
Joshua Walker
Josiah Powell
I haven't been keeping up with the show for a long time now, but as far as I've seem they only understand the concept of obsession.
Cooper Howard
With the good old murdercock
Jacob Nguyen
Juan Butler
They don't, they only understand primal urges such as infatuation, desire, and addiction. That's the whole point of the song "Love Like You" which is all about Rose trying to comprehend the sutble nuances of human love such as compassion, selflessness, and compromise. Compare that to pearl who is just plain fucking addicted to and contact with rose that she'd run head first into harm for a chance at it and Garnet who is the literal Avatar of two people's unhealthy dependence on one another.
Leo Martin
much as i wish the show was that smart, ruby and sapphire are indeed supposed to be in true actual love.