"No man’s land" is a term from World War I; it was the dangerous area between the safe trenches.

In tennis it’s the dangerous area between your baseline and your service line. It’s dangerous because most of your opponent’s well-hit groundstrokes bounce there. When you’re positioned here, shots bounce at your feet or behind you.

It’s better to be a step behind your baseline or up at the net position.

When trading groundstrokes with a competent groundstroker, stay back if you want to rally and go up if you want to volley. Indecision will be costly.

Of course, you will often have to pass through "no man’s land" but you don’t want to play there by choice.

If the net is your goal, be patient; wait for a short ball from your opponent (around the service line). Move forward a few steps, stroke an approach shot down the sideline and go. Don’t wait to see how good your approach shot is, by then you’ve lost valuable time and positioning; commit beforehand.

Players who hesitate will spend time in "no man’s land."