Spring has a tendency to store energy in them and deform its shape when force is applied on it. Once the applied force is removed it regains its original shape and size.
It is in helical shape and is used in mattress to give structure and support. Spring have elastic nature and follows spring forces, F = k * x
where is the applied force, k is the spring constant and x is the amount of extension.
When a heavier person sits on a mattress, more weight is applied on springs and they form coils, as weight is removed they regains its shape again.
