The "aside" element is a section that somehow related to main content, but it can be separate from that content. In this tutorial, I use "aside" element for tips related to the topic. What mentioned in the the yellow block provides additional information to reader, however, a reader can actually continue the tutorial without reading the tips.
The specifications of W3C says:
The aside element represents a section of a page that consists of content that is tangentially related to the content around the aside element, and which could be considered separate from that content. Such sections are often represented as sidebars in printed typography.
The element can be used for typographical effects like pull quotes or sidebars, for advertising, for groups of nav elements, and for other content that is considered separate from the main content of the page.