New players sometimes have difficulty determining if the ball is in bounds or out of bounds, especially players who have played tennis for many years. The rules for tennis are different than the rules for pickleball. Here is the verbiage and an image from the 2018 official rulebook.
6.C. A ball contacting the playing surface outside of the
baseline or sideline, even though the edge of the ball
overlaps the line, is considered out of bounds (see the
Hopefully this guideline will clarify the rules.
Click Here to view a video about line calls.