Before you start to wonder how you will get time off from work to keep a Sabbath for a whole year, note that the sabbatical year is not a Sabbath for people, it is a Sabbath for the land of Israel. The Torah instructs the children of Israel to let the land of Israel rest by desisting from agriculture for one out of every seven years. Farmers in the land of Israel were instructed to let the land go fallow. They were not to plow, sow, prune, reap or trim during the seventh year. They could pick and eat the crops that grew of their own accord, but that was to be the limit of their agricultural production.
This does not mean that people in North America or Africa need to let their gardens and fields go unplanted or untended during the sabbatical year. The sabbatical-year laws apply only to agriculture in the land of Israel. That is why the Torah says, "When you come into the land ..." before introducing the sabbatical-year law.
Why does the land of Israel need to rest? Does it get tired? The word shabbat (שבת) does not mean "to rest" in the sense of taking a nap or getting some relaxing time by lounging around for a while. The main idea behind the word shabbat is "to cease" or "to desist." The Sabbath a day of ceasing from production and creation. So too the land of Israel was to have a year of ceasing from production.
It is easy to fall into the trap of believing that if we did stop working, the world will stop spinning. The Torah seeks to teach us to place our trust in God rather than our own efforts. Imagine having a year off, once every seven years, to devote yourself to studying the Scriptures, learning Torah and serving the kingdom.
The anticipation of the coming sabbatical year transforms the other six years. Rather than simply mundane agriculture and production, the six years work toward a goal: the sabbatical year. The sabbatical year teaches that even our normal occupations and vocations should be working toward the goal of the kingdom.
A person may not think of his job as particularly spiritual or godly. For example, suppose a person works as a clerk at a grocery store. His entire day is spent scanning purchases, punching a cash register and making change. Nothing very holy about that, and grocers do not get a sabbatical year. However, when he remembers that he is not simply working for a paycheck but that he is working with the goal of serving the kingdom, his mundane job becomes meaningful. With the money he makes from the job, he supports his family, gives to charity and affords a Sabbath day that he can give to the LORD. He is not just working for a paycheck, he is working for the kingdom of heaven.