HiDPI

HiDPI means high dots per inch. In BetterDisplay's mode lists, it identifies high-resolution rendering that gives interface elements more pixels at a given logical size. LoDPI identifies the corresponding low-resolution mode.

For a worked comparison, see HiDPI versus LoDPI at the same desktop size.

On macOS, high-resolution modes commonly use two backing pixels per logical unit in each dimension, while ordinary modes use one. This is a rendering scale, not a measurement of the screen's physical pixel density or a complete description of its final native resolution. Apple’s backing-scale documentation

A suitable HiDPI mode can give you sharper rendering at an interface size that is comfortable to use. BetterDisplay lets you filter the mode list by HiDPI or LoDPI, but a filter only selects among available modes; it does not create unsupported ones.

See Resolution for desktop size, Flexible scaling for generated choices, and Display Mode for the mode choices.