Qt has a reduced version of HTML and CSS that it uses for Widgets styling, which is why you can make words bold, or underlined or whatever, in labels and pretty

Qt has a reduced version of HTML and CSS that it uses for Widgets styling, which is why you can make words bold, or underlined or whatever, in labels and pretty much everywhere in the GUI. This is very useful to have. Many more basic toolkits include no such functionality, or have a divide between "plain text" widgets, which can do no formatting at all, and a real browser-ish HTML widget. (There's also capital-R-T Rich Text used in some parts of Windows but you really don't want to go there)