Shavua Tov. In פרשת בשלח we have a reference to תחום שבת. We are not supposed to leave the city limits on Shabbat up to 2000 אמות or cubits. The Rabbis made up the concept of עירוב תחומין where one puts food 2000 אמות out of the city before Shabbat. If the traveler stops to eat that food on Shabbat, he's awarded another 2000 אמות.
There is a practical application where a person might be in a non-religious Yishuv on Shabbat and the nearest Minyan is in another Yishuv a few miles away. He makes this עירוב תחומין before Shabbat in order to reach his destination within Halachic boundaries.
The mystical reason for this according to the של״ה הקודש, is that if we remain stationed in one place, Shabbat is the perfect time to break up קליפות, or negative barriers, that prevent us from coming closer to Hashem. Leaving our domain minimizes our ability to break the קליפה.