Meaning
A hand with the index finger raised and the palm facing the viewer. Literally it points up, but it often means one, or one moment.
It can say “wait a second”, “one more thing”, “number one” or make a point in an argument. It also marks the first item in a list. Unlike 👆, the palm side faces you. Skin-tone versions exist. Example: “One sec, finishing this email first ☝️”.