6 Basics [basic]

6.7 Memory and objects [basic.memobj]

6.7.5 Storage duration [basic.stc] Static storage duration [basic.stc.static]

All variables which do not have dynamic storage duration, do not have thread storage duration, and are not local have static storage duration.
The storage for these entities lasts for the duration of the program ([basic.start.static], [basic.start.term]).
If a variable with static storage duration has initialization or a destructor with side effects, it shall not be eliminated even if it appears to be unused, except that a class object or its copy/move may be eliminated as specified in [class.copy.elision].
The keyword static can be used to declare a local variable with static storage duration.
[Note 1:
[stmt.dcl] describes the initialization of local static variables; [basic.start.term] describes the destruction of local static variables.
— end note]
The keyword static applied to a class data member in a class definition gives the data member static storage duration.