What is moment of inertia?

Put in basic terms the moment of inertia is the resistance of a body to angular acceleration. For example if you had a shaft with a mass on one end maybe a heavy ball or disk. If you tried to rotate that shaft in your hands to angularly accelerate it you will feel resistance to the rotation. Depending on the geometry and weight of the mass the resistance will be greater for certain objects than others. This is due to the objects moment of inertia. So moment of inertia is calculating, based on an objects geometry and mass, how much torque would be required to angularly accelerate that object. The equation for angular acceleration is T=Ia where T is applied torque, I is moment of inertia, and a is angular acceleration. This equation is similar to that for linear acceleration F=ma. Hope this helps.

While in you're in a car and th car suddenly accelerates, you feel like you're being pulled back. That's inertia.

It's your body's resistance to the change of the car's pace.

The Moment of Inertia of a cross section (of a support beam) is used to calculate bending stresses in loaded beams and support members as follows:

The expression for bending stress is S = Mc/I where S is the bending stress, M = the bending moment in the member due to the applied loads, at the point where you want to determine the stress, I = the Moment of Inertia of the cross section of the beam, c= the dimension from the centroid of the cross section of the beam to the point at which you want to determine the stress.

when an object moves from a stand still to moving when a force acts on it to overcome its weight.