Have you ever observed, water flows easily when compared to ghee, coconut oil, honey, etc? This is because the relative force between different layers of water is less when compared to the relative force between different layers of ghee, coconut oil, honey, etc...This is called viscous force.
When a liquid flows, there is a frictional force between different layers of the liquid, if this force acts in a reverse order to stop the relative motion between layers of the liquid it is referred to as viscous force.
This property of any liquid is referred to as viscosity.
Viscous force is measured by Nm2 in S.I. units.
 where, N stands for newton.
In CGS Unit the viscous forces is measured as  Poise(P) or Pouseuille(PI) named after famous mathematician Jean Poiseuille.
1 Pa.s = 10 Poise
Friction is a type of contact force, that is if the friction between your hand and the glass is high, then you can hold the glass firmly (or) with more grip.
Have you ever got scolding from your mother for dropping a glass of water, you took it properly but since your hands were oily (or) you ate oily food before, because of the friction between your hands and the glass reduced by the oil.
Highly viscous liquids such as oil, ghee can reduce the friction between the objects easily. Friction is possible between two moving bodies (or) two bodies that tend to move. Friction always acts in a direction opposite to the moving bodies.