Henotheism is a belief in religions (like
Hinduism) which recognizes a single
deity, but recognizes he/she within other gods and goddesses as facets or manifestations or aspects of that
supreme God, in the example of Hinduism,
Brahman.
This also can mean, like Frater_219 said, that
some people worshipped only one deity, but whose neighbors worshipped other ones
For instance, in modern Hinduism, there are two main branches-
However, ancient Hindus, or rural ones of today usually also worship their village god or goddess and/or their earth goddess.