Traditionalists are a group of humans who have chosen to live their lives in what they consider a more "traditional" way. It excludes most forms of contemporary 24th century technologies and conveniences.
There are several specially designated areas on Earth where people who have chosen to adapt this sort of lifestyle can live. Such areas are restricted to most forms of modern technology, though access to them is free. Certain planets within and outside of the Federation are colonized fully or partially by Humans wishing to live in this lifestyle.
Certain of these areas do allow a certain level of technological improvements, meaning that not all these areas completely prohibit technology. The various view on what constitutes a "traditional" lifestyle may vary from region to region and their respective cultural background.