Why are viewport and screen size different?

Screen size is your physical monitor. Viewport is just the area of the web page (excluding browser bars). Responsive design cares about viewport.

Modern screens pack more pixels into the same space for sharpness. A ratio of 2 means there are 2 physical pixels for every 1 CSS pixel.

No, this information is just read from your browser to show you. it is not recorded.

Screen Resolution Info - Free Online Tool

Name: Screen Resolution Info
Availability: InStock
Rating: 4.8 (1250 reviews)
Author: UtilToolkits

Title Case and Sentence case have different vibes. Title Case is great for headlines, while Sentence case is more casual and readable for paragraphs.