Some articles on this site use symbols on the right margins to indicate the type of content and allow readers to skip possibly uninteresting or complex part
How Things Work: the cogs mark sections that detail how a particular process woks
Geeky Stuff: The test tube stands for geeky content. Something that is cool to know but only has little importance in practical home brewing.
Practical Brewing Advice: The pot stands for practical brewing advice that will help you in home brewing. Oftentimes a conclusion that is drawn from preceding, more complex, content.
Brewing Basics: The building blocks stand for basic stuff that is important for the understanding of further discussions and elaborations.