TIFF is the workhorse format for professional imaging, scanning, prepress, archival photography. It supports lossless compression, multiple pages per file, layered data, and 16-bit-per-channel color depth (vs 8-bit in JPG/PNG). Files are large; the tradeoff is fidelity. Most consumer software doesn't display TIFF in browsers, which is why archivists frequently convert to JPG or PDF for sharing.
How to open
macOS Preview, Windows Photos, and most professional image editors (Photoshop, Capture One, Lightroom) read TIFF. Browsers generally do not display it inline; you'll need a viewer or to convert.