Why does the graph of a square root function look like half a parabola?

Square root is the inverse of squaring something.a basic parabola  squares the input.a basic square root function  square roots the input.  for example, on , the coordinate  is related to the coordinate of  on  .an input of 2, put into , outputs 4. if you use that output as an input into , you will get the original input of 2.and for coordinates like  on the parabola corresponds to  .  as for why is half a parabola:   technically, the relation  gives a full sideways parabola (to graph it, graph and at the same time.)  but it is not considered a function; a function needs to pass the "vertical line test."  square roots of negative numbers are not defined, so the basic  will only give positive answers, thus looking like a bisected parabola.for  , if you cut the parabola in half so that the domain is  , then the inverse function (the function that "undoes" the output of  )  will be the typical  graph. i have attached a picture of this.