What is resistance and its types?

Hint: In the question, we are asked to define the very basic physical quantity that is resistance. One could define it and also give the different types of resistors that you know. You could make use of Ohm's law so as to define the quantity. Also mention the unit in which it is measured.

Complete answer:
In the question, we are asked to explain what resistance is and also give its different types. So, as a first step, let us explain what exactly resistance is.
Resistance could be defined as the measure of the opposition that is offered to the flow of current in a particular electrical circuit. This quantity is measured in Ohms which is also its SI unit and is given by Greek letter omega$\left( \Omega \right)$.
We could classify materials into conductors and insulators by the resistance offered by them. So, the materials that have very little resistance are conductors and the ones with very high resistance are insulators.
From Ohm’s law, we could also define resistance as the ratio of applied voltage to the current flowing through the material.
Now, the classification of resistors is done basically into two major types. They are variable resistors and fixed resistors. From their respective name itself we get the basis of classification. The one in which the resistance is fixed is fixed resistance and the one in which it is varied is variable resistors.

Note: The higher the magnitude of resistance is the more would be the current flow, which is quite obvious from the very definition. Burning and corrosion of conductors may lead to them having high resistance values. Also, the insulators damaged by moisture or overheating may also have lower resistance values.