I know… a fair amount… about a lot of things:
– sailing (in very general terms), including ropework, knots and splicing techniques;
– Microsoft Excel and Access, including VBA (visual basic for applications – macros, in a word);
– language (specifically the English language), including spelling, vocabulary, grammar, usage and syntax, some etymology;
– industrial construction, specifically coal-fired power boiler erection, welding and nondestructive examination, the ASME Boiler and Pressure Vessel Code (Section I);
– logic, logical argument and analysis (including a passing familiarity with most of the common logical fallacies)
And maybe a bit more. But I don’t consider myself any kind of expert in any of those things. Better than some, maybe, but I know better examples in every single field.