A known volume of 0.1 M solution of hydrobromic acid is reacted with 25 mL and the concentration of the potassium hydroxide is calculated from the stoichiometry of the reaction. Then, we could use the fact that the molarity of a reaction is equal to the moles of the solute divided by the liters of the solution, so we could replace the values that we know and find the value of the concentration.
Remember that:
Titration is a kind of reaction in which the concentration of an unknown solution is determined by reacting a known volume of this solution with a known volume of a standard solution and carrying out the necessary stoichiometric calculations in order to obtain the concentration of the unknown solution.
And, the volume of 0.1 M solution of hydrobromic acid required to reach end point is used calculate the concentration of the potassium hydroxide solution.