每个人都在同时写作，每个人都会得到价值他/她设置或差异？

是。

每个客户端都是独立的 - 您甚至可以在同一浏览器窗口中为三个不同的选项卡获得不同的结果 - 每个客户页面都有自己的Session。结果将特定于每个用户。

"everybody is writing at same time,everybody will get value he/she set or diff?"
Yes.
Each client is separate - you'd even get different results for three different tabs in the same browser window - and each client page has it's own Session. The results will be specific to each user.