What is the meaning of -chan?

Appended to a person's name (usually a female, child, a close friend, or an intimate) to add politeness. It is sometimes used to denote cuteness or familiarity.

Used in the names of imageboards, usually ones that try to emulate 4chan.

forms verbal nouns from first-conjugation verbs ending in -igh

Rōmaji transcription of ちゃん

allomorph of -tan used for stems that end in i

Source: wiktionary.org