This is used to provide higher resolution thumbnails for high pixel density displays, such as phones or laptops. If your screen has a 2x pixel density ratio, then 360x360 thumbnails will be rendered at 720x720 resolution. We use WebP here because it's about 15% smaller than the equivalent JPEG, and because if a device has a high enough pixel density to use this, then it probably supports WebP. 720x720 thumbnails average about 36kb in size, compared to 20.35kb for 360x360 thumbnails and 7.55kb for 180x180 thumbnails.
Components
Components are used to encapsulate common UI widgets used throughout the site. This includes things like comments, tag lists, post thumbnails, paginators, and other things used repeatedly throughout the site. Components encapsulate a widget's HTML, CSS, and Javascript together so that all the code for a component is in a single place.
This uses the ViewComponent library.
Components are similar in concept to React components.