In this video the different types of number system is described. In this video the rational and irrational number , integer, whole, natural numbers have been described. Moreover the explanation of infinity and undefined also has been explained in a simple manner. The different types of errors also has been analysed. truncation error, chopping, rounding, are the different types of errors. When using numerical methods or algorithms and computing with finite precision, errors of approximation or rounding and truncation are introduced. It is important to have a notion of their nature and their order. A newly developed method is worthless without an error analysis. Neither does it make sense to use methods which introduce errors with magnitudes larger than the effects to be measured or simulated. On the other hand, using a method with very high accuracy might be computationally too expensive to justify the gain in accuracy.