Jesse originally approached Rachel to try and reunite her with her biological mother and quickly fell in love, even though he wasn't supposed to. The two of them are arrogant drama queens who are driven as hell and often feel separated from other people. As Rachel said, 'their deep respect for each other's talent will carry them through.' As the stars of two rival Glee clubs, the two had a lot of enemies.
Obviously tortured, Jesse was forced to break an egg on Rachel's head, and didn't show his face until about a year later when he returned from college to apologize. Rachel accepted and hinted that all was not lost for them as a pair, but alas, the writers of Glee are total morons and so they didn't end up together and Rachel was allowed to become the pathetic, whiny bitch she never was with Jesse.
J: "And miss all your drama? Never."
"I don't know why all these people like Finchel, it's toxic. St. Berry brought out the best in both characters, had far more chemistry, and understood each other better."