How to create this kind of theorem box? (LaTeX TColorboxes)

[SillyFreak]

@Andrew, while all of these packages seem relevant, I couldn’t see directly in any of their readmes how to achieve the result OP expects. Please add some context and/or concrete applications (i.e. code) to your answer, as per the answering guidelines:

@reknih

If a question is answered in an existing resource, explain how it solves the problem. Write as if OP had seen that resource, but not managed to apply it to their specific situation.