For the #profile-form when a user submits, it replaces the contents of #profile-name and #profile-description with whatever the user typed into #profile-name-input and #profile-description-input
When the #activity-form gets submitted, it adds the a new activity as a <p> tag to the #activities-container.
When the #cool-point-form is submitted, it adds to the #cool-points span.
When the #cool-multiplier-form is submitted, it multiplies the number of cool points in #cool-points by the submitted amount.
When the #picture-form is submitted it takes the submitted URL and creates and appends a new <img> that shows the picture for the URL.