An accent is a stress or emphasis on a particular part of something, usually a word. Pronounce the word "doofus" with the accent on the first syllable: DOO-fuss.
Accent comes from the Latin accentus, which means "the intonation of singing." We use accent for different kinds of emphasis in speech. In some foreign languages, the mark above a letter is an accent that signals how to pronounce it. If you accent something, like the "t" on the end of your name, you highlight it. In music, an emphasized note is accented. A regional accent is the particular way that people from that place speak.