What does Exodus 31:15 mean?

You can work for six days, but the seventh day is a day of complete rest, set apart for the Lord. Anyone who does any work on the Sabbath must be put to death. Exodus 31:15 - Modern Text Bible

(God repeats the pattern: six days for work, one for rest. The penalty for breaking this is severe, underlining how important rest and trust in God are.)