You use holiday (or holidays) in British English and vacation in North American English to describe the regular periods of time when you are not at work or school, or time that you spend travelling or resting away from home:

I get two weeks’ holiday/vacation a year.
He’s on holiday/vacation next week.
I like to take my holiday/vacation in the summer.
the summer holidays/vacation

the summer holidays/vacation
In North American English a holiday (or a public holiday) is a single day when government offices, schools, banks and businesses are closed. In British English it is called a bank holiday:
The school will be closed Monday because it’s a holiday.