We handle filter conditions for date or date and time, such as Today, This week, This month, and This year in the following ways.

Today, Yesterday, and Tomorrow: The starting point for the period is the day you perform the filter action.
This week, Last week, and Next week: The starting point for the period is the week you perform the filter action. The date range of the week is set from Sunday to Saturday of the specified week.
This month, Last month, and Next month: The starting point for the period is the month you perform the filter action. The date range of the month is set from the first day to the last day of the specified month.
This year, Last year, and Next year: The starting point for the period is the year you perform the filter action. The range of the year is set from January to December of the specified year.

The displayed options might differ (Next week and Next month, or Following week and Following month) depending on the setting screens, but the same idea is applied.
What is the difference between the "Next week" and "Following week" conditions, which are used for filtering "Date" and "Date and time" fields?