In my experience, a method of determining the concentration of an unknown substance by adding amounts of a standard solution, that is, one whose concentration is known. The only practical lab experience which I have had with titration is an acid-base titration. The idea is something like this: one has an acid of an unknown concentration and a base of a known concentration in two graduated burettes. One adds an amount of the acid and an amount of an indicator (the indicator should be provided by whoever set up the lab since only he or she will know what pH range is appropriate) to a solution. One then adds the base until whatever color change the indicator will undergo happens. One then attempts to return the solution to its original color. Once the solution can change color with one drop of either solution, the solution has reached the end point. The end point represents the point in the chemical reaction in which the concentrations of both substances are equally. This, obviously, does not mean that the volumes are the same, but they could be. By recording the volume of each substance added, one can then perform several stoichiometric calculations the find the concentration of the unknown solution. Please excuse me if this write up is inaccurate, I'm just a high school chemistry student.