Viscosity is like the friction of fluids. Just like friction, it is the tendency of a fluid to resist motion. This can be seen when something like honey is poured on a table against water. The honey slot creeps towards the edge of the table while the water runs over quickly. This is because of the difference in viscosity of the two fluids.

Viscosity is a fluid property cause by two major reasons

1)Intermolecular force of cohesion: Due to strong cohesive forces between the molecules,any layer in a moving fluid tries to drag the adjacent layer to move with same speed ,producing effect of viscosity.

Molecular momentum exchange: The individual molecules of fluid are continuously in motion and this motion makes possible the process of exchange of momentum between different moving layers.