The circumfix is a type of affix with two parts. It has one placed at the beginning of a word and another at the end. English doesn't have circumfixes, but they occur in other languages such as Dutch, German, Georgian, Hungarian and Malay.
The circumfix is often seen in the German past participle. For example, the infinitive sagen (to say) has the past participle gesagt. The two parts of the circumfix are ge- and -t. Dutch has a similar system. For example, the Dutch equivalent of sagen is zeggen. The Dutch participle is gezegt. As in German, the two parts of the circumfix are ge- and -t.
In Hungarian the superlative of adjectives is formed with a circumfix. The Hungarian word for big is nagy. The comparative is nagyobb, but the superlative is legnagyobb. Here the two parts which form the Hungarian circumfix are leg- and -obb.
Thoiugh the circumflix isn't used in English, it is in other languages. German and Dutch often use the circumfix to form past participles and Hungarian uses it to form superlatives. It's a type of affix that is less known than the prefix, suffix and infix.