It looks like a basic issue but I haven't found an answer anywhere.
Please tell me why the behavior (after clicking) of this Button
:
Button["X", Print@1; Pause@1; Print@2;]
(*1 and 2 appear simultaneously after 1 sec*)
is different from the behavior of Shift+Enter evaluation:
Print@1; Pause@1; Print@2;
(*printing of 2 happens 1sec after 1*)