Pearl and Rose have a long complicated romantic and codependent history with one another. Pearl considers herself closer to Rose than any of the other Crystal Gems.
At the very start of the series, Pearl is alone and Rose is dead. The audience catches glimpses of what their relationship used to be like through flashbacks and through Pearl's words. There is also tension between Pearl and Greg due to the fact Rose died giving birth to Greg's child, and Pearl both feeling jealous of the affections Rose gave Greg and heartbroken by the loss of Rose.
When Pearl learns about Lion and that there were things Rose didn't tell her, she has a breakdown and isolates herself. When Steven confronts her, wondering what he did wrong, and hugging her, Pearl wonders aloud: 'What would she think of me now? Sometimes I still think she's watching me through your eyes'. Steven replies, 'I don't know, but I think you're pretty great.'
Throughout the series, Pearl is greatly effected by the loss of Rose. Grief fuels many of her actions, as she misses Rose and dedicated her life to serving her as a 'knight'. When trying to teach Connie how to sword fight she brings some of this baggage to the table and inadvertently teaches Connie that 'when you live for someone / you're prepared to die'. Throughout the song, flashbacks are shown, and it is clear Pearl is talking about her relationship with Rose. Steven stops this training from continuing as unhealthily as it was and both kids ask Pearl 'did Rose make you feel like you were nothing?' Pearl replies, 'No, she made me feel like I was everything.'
During flashbacks we can see Pearl immediately becomes jealous when Greg enters the picture. 'He can sing!' says Rose. 'I can sing!' replies Pearl huffily. Pearl tries to show Greg there is something special between her and Rose exclusively by fusing with Rose in front of Greg and dropping a mic. Pearl also has nightmares of Rose and Greg being together, and has a tendency to act cold towards Greg due to this.
In special musical episode "Mr. Greg", Pearl sings a song about her grief surrounding letting go of Rose's death. "It's over isn't it? Why can't I move on?" Hearing all this causes Greg and Pearl to have a hard time
talking, but Steven brings them together by telling them he loves them both and they both love him. With this, Pearl is finally able to not resent Greg as much.
Pearl also seems to 'have a type' for people who look similar to Rose. In one episode she gets someone's number and they are also large, with pink puffy hair. 'I didn't know humans could have hair like that' is something Pearl says.
Later in the series it is revealed Rose was Pink Diamond and that she commanded Pearl to secrecy so that she couldn't speak about her identity which is something Pearl has had to struggle with throughout the series.
It is the second most popular Steven Universe ship on Ao3, and the most popular ship involving both characters.
The ship has some controversy due to Pearl's status on Homeworld and especially in light of the reveal that Rose Quartz was Pink Diamond. Pearls are treated as slaves on Homeworld, and the fact Pearl worked directly for Rose before raised some questions for some viewers.