A shopping cart full of groceries.
A shopping cart full of groceries will have more mass than a empty shopping cart.
Inertia is the tendency of the object to resist the change in its state.
If it is at rest it will remain at rest unless an external force is applied, or if it is moving in a straight line it will be in same motion unless being stopped by an external force.
Usually the friction offered by the surface (road on which we are moving the cart), is the force that acts as the external force to stop the cart.
To change the state of rest of the cart filled with groceries, we will need more force as compared to that required to change the state of the empty cart.
Therefore the inertia of a shopping cart full of groceries will be more.
Inertia can be said to be the measure of mass. More the inertia more will be the mass.
Or it can be said: mass of an object is the quantity that solely depends upon its inertia. A more massive object will have greater tendency to resist the change in its state ( rest to motion or motion to rest).