Yogh is shaped like the Arabic numeral 3, which is sometimes substituted for the character in online reference works. It would seem there is some confusion about the letter in the literature. The character yogh - pronounced either [jouk], [joug], [jou] or [joux] - came into Old English spelling via Irish. It stood for /g/ and its various allophones - including the velar fricative [G] (voiced [x]) and [g] - as well as the phoneme /j/ (y in modern English spelling). In Middle English, yogh stood for the phoneme /x/ as in niȝt (night, then still pronounced as spelled: /nixt/). Sometimes, yogh stood for /j/ or /w/, e.g. in the word Ȝoȝelinge = /'jowelinge/ = yowling. In the late Middle English period, yogh was no longer used: niȝt came to be spelled night. Middle English used the French g for /g/.
In Unicode 1.0 the character Yogh was mistakenly unified with the quite different character Ezh (Ʒ/ʒ), and Yogh was not correctly added to Unicode until Unicode 4.0.