Answer:
Ideal mechanical advantage does not considers frictional losses of force into account whereas actual mechanical advantage does.
Step-by-step explanation:
Mechanical advantage is the increase in the output force by a simple machine which is due to increased arm length on which the output is desired. This is in accordance with the law of conservation of energy and moments.
Mathematically give as;

where:
are the force due to load and effort respectively.
are the length of effort arm and load arm respectively.
Now the mechanical advantage:

In practical cases we are not able to take the full advantage of this multiplied force due to the frictional losses.