Typography basics: readability, legibility, and impact

I am reading an article in Layers Magazine with a good summary about the basics of typography:

• Readability: how easy is it to read a long block of text
• Legibility: how easy is it to recognize short bursts of text instantly
• Impact: what emotional reaction does a type face provoke

I often use all caps in PowerPoint. It was interesting to read that all caps forces the brain to read the word letter by letter before it can be recognized, while with regular type a word gets identified instantly.