Elements of an array should be of the same kind:
 

An array of dogs:
 

Butch	Rex	Timothy	wally	Cord
1	2	3	4	5

 

An array of cats:
 

Fluffy	Missy	Felix	Tom	Otis
1	2	3	4	5

 

Not an array of cats and dogs:
 

Butch	Missy	Rex	Felix	Timothy
1	2	3	4	5