This Book Provides the basic knowledge of the various fundamental spaces of test functions and their duals i.e., spaces of the generalized functions.The distributions are also known as generalized functions. Some authors make a little distinction between them which has been pointed out in chapter II of the book. They are members of dual spaces of certain locally convex vector spaces of complex - valued infinitely differentiable functions defined on open subsets of Euclidean Spaces. Thus one who intends to know the distribution should be acquainted with the properties of vector spaces and also of topological spaces. Wondering in the field of distributions whatever I could learn and observe has been incorporated in this book.