Why and when i should access to an object through pointer ????!!!

Question

this is confusing a little bit please i need explanation (why and when??)

Answer 1

mouse pointer ?
clicking , mouse-hovering , cursor displays.

linked-list or array pointer ?
well , when you had thousands to Billion of data ,
you will notice that array alone costs too much data space and reducing performances , thing like linked-list helps alot to compress data usages , faster performance , but harder to code than ordinary variable or array.