The separation barrier that separate the Gaza Strip and Egypt continues to be an issue for the residence of the narrow strip. The project which was finished in 2005 prior to Israel’s Gaza pullout
The area borders Israel on the north and east, and entry into Israel is possible only at crossings under its control. Access to and from the Gaza Strip by sea, to the west, and by air, is under Israel's exclusive control. (For more info about the crossing and Israel read B'Tselem)
Israel built a barrier and 200–300 meter buffer zone in the Philadelphi corridor, that’s the distance a bus has to take you from the Palestinian side
To travel out of Gaza, all residents have to sign up with the local government who in turn reject your departure--mostly in criminal and political grounds.
The Egyptians share the info they get from the Palestinians with the Israelis and thus there is a lit of about 20 k to 50 thousand names on that list for people who cannot travel out of Gaza. Some of those on the list can also be criminal or drug deals with some crimes in Egypt. but the majority are people who might have affiliation with militant Palestinian groups.
And there is another list that Fatah helps put for people they do not like, the Mubarak men used to believe anything Fatah said, but this is not true right now.
Some people who are banned from entering Egypt or traveling through it--most Palestinians are not allowed into Egypt, but rather transported to the airport with police escort, a service many Gazans have come to actually enjoy, travel underground through the tunnels on the borders. But this service tends to be shady and not much info about the operation of tunnels is available.
To sum, to travel those 200 to 300 meters, Palestinians have to be given the green light from Hamas, Fatah, Israel and Egypt too. I have gone through this process few times and it's not easy--travel is not easy by nature, but this can be one hell of a humiliating experience that requires patience, resilience and a great deal of luck