An expo is a big public show where companies, countries, or makers put their work out for people to see. It is a short, easy form of exposition in the “big fair” sense, not the “long explanation” sense. You go to a trade expo to see new products, or to a world expo where countries show themselves. On posters it often appears as Expo, as if it were a name. People say it in speech and on signs; the long word exposition sounds stiffer.

博覽會；世界級的說「世博」，口語也常直接說 expo