When they say, e.g. "a six-figure salary", do they mean a person earns that much per month or per year if no further details are included?
As a general rule, salaries are expressed by the year but then paid by the week, half-month, or month.
Wages are expressed and paid by the hour.
This may differ by country. In the US, “exempt” (salaried) employees — typically well-paid white-collar workers — are paid a fixed amount every pay-period. They are exempt from overtime, they do not punch in, they are not docked for arriving late or leaving early, and they receive vacation time, sick time, or “paid time-off” (PTO). “Non-exempt” employees — typically blue-collar workers — have rigidly scheduled work-days, punch in, are paid by the hours actually worked, have (according to local law) scheduled meal- and rest-breaks, are paid a higher rate (at least 1.5x) for overtime, and receive “wages” not “salaries”.
There is no default. A salary is the money that an employer agrees to regularly pay a worker. If someone says, "My salary is $10,000", what the term is for the $10,000 depends on which country they're in, even if they're speaking English. When I work in North America, "my salary" means the yearly amount. But when I worked in South Korea and Turkey, "my salary" meant the amount I was paid every month.
A salary is an annual amount agreed upon between company and employee and paid to the employee in increments on a schedule for work performed in a specific role. Source
So yes usually salaries are per year, plus a six figure is a lot of money that most people cannot get in a month!