by which we take input from user and by which we display

Answer 1

Prompt() is used to take user input, also it takes two parameters.

alert() is used to display text or massage which you want to display on user's screen.

Answer 2

yes right prompt box is a good methot to take an input and for output you can use many things
1. prompt box itself Prompt ("Output");
2. alert ("output");
3. confirm ("output");
4. document.write ("output");