Your website's favicon
The favicon is the small icon in a browser tab and on a phone's home screen. You have three options. Follow my design uses whatever the design provides, which is the safe default. Use my initials draws your initials in your own colors, which reads better than most logos at sixteen pixels. Or upload your own, in which case use a square image with one strong shape in it. A headshot does not work here: at this size a face becomes a smudge, and a letter or a mark stays readable.