Declarations is when you tell the compiler I want a symbolic name of this variable, but you dont give it a value.
Example
int myballs;Multiple Declarations at once
If multiple variables/functions have the same datatype, they can be declared at the same time
Multiple variables
int a , b;Variables and functions
double sum, atof();You are not able to declare multiple functions on one line!
Garbage Values
if Automatic Variables or Register Variables are declared and not Initialized, then you get garbage values Undefined Behaviors