The most important input type: Forms
With our attention spans decreasing everyday, we cannot have stand alone websites /applications anymore. We need user input. We want the user to interact in some way.
Many a times, we need some kind of input from the user, it may be in the for of feedback, or some information for going further. Forms are one of the places you will spend a lot of your time, usability wise. They cause confusion, mistakes, and loss of engagement, and that they are one among the foremost valuable parts of your site.