Tanto (n)text, (var)binary e image son tipos de datos binarios.
Cita:
Iniciado por BOL Binary Strings
binary
Fixed-length binary data with a maximum length of 8,000 bytes.
varbinary
Variable-length binary data with a maximum length of 8,000 bytes.
image
Variable-length binary data with a maximum length of 2^31 - 1 (2,147,483,647) bytes.
BLOB es el equivalente en otros motores y lenguajes.