The meaning of "8 items bought on Ctrip, need to be used collectively" is: "The 8 items purchased on Ctrip need to be used together."

“What does it mean that the 8 items purchased on Ctrip need to be used together?” This sentence means that the 8 items or services purchased on Ctrip need to be used together and cannot be used separately. “Collective use” here means that these services or items must be used simultaneously and together to achieve a certain effect or complete a certain purpose.