Crew Dragon will spend five days docked to the ISS and on March 8 it will return back to Earth and land in the Atlantic Ocean, which will be another key test to assess the spacecraft's safety. Boeing and SpaceX are separately working on manned space flight ability for NASA. The US hasn't been able to launch manned missions since the retirement of the Space Shuttle in 2011, and had to rely on Russia's Soyuz spacecraft.
Further details can be read at Space.com. If things go well with the current mission and a subsequent in-flight abort test in June 2019, SpaceX may be able to fly its first crewed test flight in July 2019.
Nobody is aboard Crew Dragon on this six-day flight, known as Demo-1, save a sensor-laden dummy astronaut named Ripley in an apparent nod to the sci-fi film "Alien." But if all goes according to plan with Demo-1 and a subsequent emergency-escape test, SpaceX will use the capsule to ferry two astronauts to the orbiting lab as early as this July.