Immobility is the state of not being able to move around. If you fall out of a tree and break your arms and legs, then you will have to put up with months of immobility while your bones heal.
Immobility could mean the condition of not being able to move, like that poor mouse stuck in a glue trap whose immobility will lead to its starvation. Immobility can also just mean the state of not moving. If you are entranced by a beautiful sunset, you might stand with quiet immobility while watching the sky.