All the fluids in actual practice are real fluids.

Fluid dynamics:

we use ideal fluid in 2 equations :

1.Continuity equation

2.Bernoulli equation

3. Newtonian Fluids:

A real fluid in which the shear stress is directly proportional to rate of shear strain (or velocity gradient).

4. Non-Newtonian Fluid:

A real fluid in which the shear stress is not proportional to the rate of shear strain.

5. Ideal Plastic Fluid:

A fluid in which shear stress is more than the yield value and shear stress is proportional to the rate of shear strain (or velocity gradient).

In fluid dynamics, the no-slip condition for viscous fluids assumes that at a solid boundary, the fluid will have zero velocity relative to the boundary.

The fluid velocity at all fluid–solid boundaries is equal to that of the solid boundary.[1] Conceptually, one can think of the outermost molecules of fluid as stuck to the surfaces past which it flows. Because the solution is prescribed at given locations.

Fluid is a substance which is capable of flowing OR Fluid is substance which deforms continuously under the influence of a shear or tangential force. OR The tendency to deform continuously is called fluidity and act of continuous deformation is called as flow.Classification of fluids-Ideal FluidReal FluidFluids which don’t have viscosity and are incompressible are termed as ideal fluid such fluid do not offer shear resistance. | Fluids which do posses viscosity are termed as real fluids. These fluids always offer shear resistance.Real Fluid further classified into two types

τ=constant×(dydx)n.

• Definition: A fluid is said to be ideal if it is assumed to be both incompressible and non viscous.
• Its bulk modulus is infinite.
• ideal fluid has no surface tension.
• Ideal fluid is a substance which is unable to resist internal shear and tensile forces.
• Ideal fluid are imaginary and do no exist in nature.
• They have laminar (smooth)flow as shown in the figure.

Real fluid

• Definition: A fluid which is compressible, has viscosity and surface tension, is known as real fluid.
• Real fluids implies friction effects.
• They have turbulent flow as shown in the figure.
• Examples: kerosene, petrol, castor oil

https://www.test-and-measurement-world.com/Terminology/difference-between-ideal-fluid-and-real-fluid.html

The Fluid which is non viscous or friction-less and in-compressible is called ideal fluid.

We assume that ideal fluid is perfect fluid but fluid without viscosity is not possible or does not exist in real world so this is only a imaginary fluid.

Real Fluid

All fluid comes under real fluid because all the fluid having viscosity, compression and surface tension in its properties with a little amount of force.

-Ideal fluid: Fluids that dont have viscosity, incompressible and also resistance to shear. 

-Real fluid: Fluids that have viscosity, compressible and always be shear resistance. 

The no-slip condition for viscous fluids assumes that at a solid boundary, the fluid will have zero velocity relative to the boundary. 

I don’t understand much about the slip and no-slip condition part.