Final answer:
Newton's First Law is known as the law of inertia, describing the tendency of objects to continue their state of rest or uniform motion unless acted upon by an external force.
Step-by-step explanation:
Newton's First Law is known as the law of inertia. Inertia is defined as the tendency of an object to maintain its state of rest or uniform motion unless acted upon by an external force. This tendency is inherently related to the mass of the object, with more massive objects exhibiting a greater inertia. It is this property of matter that Newton's First Law addresses, stating that without the influence of a net external force, an object at rest will stay at rest and an object in motion will continue moving at a constant velocity in a straight line.