What does it mean that other can't be used alone? Some people like to stay at home on Sundays, but others like to go to the cinema

What does it mean that other can't be used alone? Some people like to stay at home on Sundays, but others like to go to the cinema

People are uncountable n
In this passage, others refers to those people other than "some people" above, and "the others people", which has nothing to do with the countability of people, but is a demonstrative pronoun
(my former teacher explained this, hoping to help you ^ ^)