CST stands for Central Standard Time. It is always UTC-6.
CST is standard time. While daylight saving time is in effect, the same areas use CDT (UTC-5) instead.
Right now Chicago uses CDT (UTC-5), not CST.
Where CST is used
Belize, Canada, Costa Rica, El Salvador, Guatemala, Honduras, Mexico, Nicaragua, United States.
In some of these countries CST is used only in part of the country or only part of the year.