The question of if they were or were not on a break stems from two episodes of Friends Season 3, the first pointedly titled “The One Where Ross and Rachel Take a Break,” where Ross and Rachel fought over the amount of time she was spending on her new job, and with her new handsome co-worker Mark.
Rachel suggested she and Ross take a break, which led Ross to drunkenly sleep with Chloe, the girl from the copy shop.
In “The One the Morning After,” Rachel found out, and instead of getting back together, the couple continued their on-again, off-again status until the series finale in Season 10.