What does Luke 6:1 mean?

One Sabbath, Jesus was walking through some grainfields. His friends started picking heads of grain, rubbing them in their hands, and eating the kernels. Luke 6:1 - Modern Text Bible

(This sets up a situation where Jesus’ followers are doing something technically allowed by the law—picking grain by hand—but it’s happening on the Sabbath, which will spark a debate about what’s really allowed on that day.)