Yes, frequently and often are used fairly interchangeably to mean "happening many times" or "happening repeatedly". While traditional grammar usage would indicate that "frequently" should be used to refer to something that happens on more than one occasion, and "often" should be used to refer to something occurring three or more times, in modern usage both words can be used for both.
Below are some examples showing how to use frequently and often:
-I frequently go to the movies.
-We often eat out on the weekends.
-She visits her family frequently.
-They often go on vacation together.
If you want to compare the actual difference between "frequently" and "often," it is helpful to think of it as a matter of degree. "Frequently" usually indicates more often or more regularly, while "often" usually indicates the occurrence of something at least three times. So if you're looking for a word to express the idea of something happening regularly or frequently, "frequently" may be the better choice.
In short, while "frequently" and "often" are related and may be used interchangeably in many cases, if you want to be really precise in your choice of words, it is useful to think of "frequently" as being associated with more regular or frequent occurrences, and "often" as being associated with occurring at least three times.