The act of declaring an object (including variables, statics, etc.) instructs the compiler how much storage to allocate.
All objects must be declared before they can be used.*
A declaration specifies a data type and a list of one, or more identifiers (names) to call the variables / objects
int myVar ;
int myVar, cat, dog, potato ; //4 integer variables declared
Multiple identifiers are separated by a comma. The above declares four variables of the data type int called myVar, cat, dog, potato.
*Note: Later we will see that functions must also be declared before they can be used