The tendency to give disproportionate weight to trivial issues of a larger or more complex project. In other words, prioritizing something easy to grasp or and/or is debatable.
The term comes from a fictional 1957 illustrative anecdote by C. Northcote Parkinson about a committee discussing a plan to build a nuclear power plant. In their meeting they spend the majority of their time arguing over the color to paint the bike shed in the back, because that was the part of the plan that everybody could understand.
It's always easier to focus on the trivial. It serves as both an opportunity to avoid more challenging, complex issues, while at the same time feeding the need to feel productive through dialogue and confrontation. This is as true for work teams as it is for personal projects, procrastination techniques, and relationships.