The technical definition of inertia is an object's tendency to resist changes in motion. That means if the object is moving, it wants to keep moving. If the object is still, it wants to remain still. Inertia is directly related to the amount of mass an object has. If the object has a lot of mass, it is harder to get it to move; if it is moving, it is harder to get it to stop.
People also use the word inertia in everyday conversation. It's a physics term that has entered the common vernacular. It is used to describe anyone or anything that does not seem to be moving or making progress. For example, we may say a company is suffering from inertia if it is not developing new products.
Just think about Newton's first law and that will tell you what inertia is. Any object will remain in its present state unless something forces it to change. So a body that is moving in a given direction at a given speed, for example, will keep doing so until some force acts to change its direction or speed.
Inertia, in physics, means either lack of movement altogether or lack of any change in movement, such as a change of speed. Here's the definition from dictionary.com:
an object has a weight of 720N on the surface of the earth what will it weigh when it is 3000km away from earth