A selfie is a photograph you take of yourself, almost always with a phone, and almost always so you can put it on a site or app — Instagram, LINE, Facebook, and the rest. People say take a selfie, not make one. You can also use it as a verb: she selfied in front of the tower. That verb still feels casual and a bit new. The word is young: it started in Australian English around 2002, from self plus the small ending -ie, the same friendly ending you hear in brownie. Though actually the idea is older than the word — people have pointed cameras at their own faces for a long time — but selfie is the everyday internet word, not a painter's picture of themselves. A self-portrait is art; a selfie is 'here I am'. It is informal. Teachers and news readers use it now without blinking, but you would not put it in a very serious letter.