What is the Rafah crossing and why is it Gaza's lifeline?

The Rafah border crossing with Egypt in the southern Gaza Strip is expected to open on Wednesday to allow several hundred foreign and dual nationals to leave Gaza.

More than eighty seriously injured Palestinians will also be allowed to leave in a deal said to have been brokered by Qatar.

This would be the first such evacuation since the conflict between Hamas and Israel began more than three weeks ago. It is not clear how long the border will stay open.

It has already been open for more than 10 days to allow aid into Gaza. So far more than 200 trucks have crossed the border but much more is needed.