In general infinity in mathematics exists, if a function get a certain value by increasing value of x. Then the graph of the function approaches the y-axis (without to ever 'touch' the y-axis) by increasing value of x. So inifnity means that the value of x can be optinal small or large (it depends on the function itself). The smaller/larger the value of x the more precisely the limit value is. All kinds of values of x which can be used to describe the limit value of a function are definable, in contrast to a certain number which are divided by 0, as this certain number is not clear after division (to put it crudely).