tls section

In MS Windows PE file terms, the .tls section provides direct PE support for static Thread Local Storage (TLS).
TLS is a special storage class supported by MS Windows, in which a data object is not an automatic (stack) variable, yet it is local to each individual thread that runs the code.
When the compiler directive "__declspec(thread)" is used, the data that is defined doesn't go into either the .data or .bss sections, it ends up in the .tls section.
Thread local storage lets a thread maintain separate instances of data.
Each thread within a process can have its own set of values that are guaranteed to be unique.