Emoji variants are alternate versions of a base emoji. Some variants change skin tone, gender, hair style, direction or role. Others change whether a character appears as colorful emoji or plain text.
Many variants are built from sequences rather than single characters. A person emoji such as 🧑 Person can combine with other characters to create profession or appearance variants. Some joined variants use ZWJ, explained in ZWJ emoji sequences.
Variants help Unicode support more meaning without creating a separate standalone code point for every possible design. The user usually sees one emoji, even when the underlying value contains multiple characters.
Skin tones are one common kind of variant. See skin tone emoji for how those modifier sequences work.