Adverbs of frequency indicate how often something happens. They are very useful to indicate how often you suffer from an illness or ailment. This frequency ranges from 100% (always) to 0% (never):

I always get a cold during the winter I never get a cold during the winter

Or in between:

Frequently	I frequently get a cold during the winter
Generally	I generally get a cold during the winter
Sometimes	I sometimes get a cold during the winter
Seldom	I seldom get a cold during the winter
Rarely	I rarely get a cold during the winter

These words and expressions are also used to indicate frequency:

Twice a day	You need to take these pills twice a day
3 times a day	You need to rub this on your neck 3 times a day
4 days a week	You need to exercise 4 times a week
Every 3 hours	You need to take this medicine every 3 hours: at 12:00, at 3:00, at 6:00 and so on.