Hardwoods or hard timbers are generally more durable and dense then softwoods or soft timbers although not all are harder than softwoods the main differences between them are botanical.
You are able to identify hard timber trees by characteristics such as their leaves because these types of trees have broader leaves than soft timber trees.
Hard timbers are often a darker colour than softwoods and most are denser due to thicker cell walls although again this does not mean that all are denser than soft timbers.
The main difference between a hard and soft wood is the vessels or pores in their microstructures. Vessels are like pipes running through the tree and act as conduits for water and nutrients in the outer layers of wood in a growing tree. The cells in these woods are closed so they cannot function like a conduit and this is why they have vessels where softwoods don't.
Many people like to buy hard timber furniture, wood panelling or floors because the majority are fairly dense which means if looked after well they last a long time and are more resistant to dents and scratches. These woods are also good for making really strong woodwork joints such as the mortise and tenon joint because they are often dense.