Challenger was built to serve as a structural test article for the shuttle program.
A lighter-weight orbiter was NASA's goal during the years in which the orbiter fleet was being built, but a test article was needed to ensure that a lighter airframe could handle the stress of space flight.
This is the crew that would man the shuttle. Francis R. Scobee, Michael J. Smith, Ronald McNair, Ellison Onizuka, Judith Resnik, Greg Jarvis, & Christa McAuliffe.
To get the Shuttle to the launch site they must fly it over. Typically on a 747.
Every crew must have a space shuttle. This is the Challenger
Sometimes there are things that go wrong on space shuttles, that can be fixed. For example, Apollo 13 had an explosion mid-flight and they were able to fix or modify things to get home.
But unfortunately, the Challenger was not fixable.
The failure of a rubber seal allowed part of the flame to ignite the spacecraft's giant fuel tank. We have learned to double check the functions and state of every single piece of the shuttle before launching.
.There was no real technological advancements for this mission
Because of the Challenger we have learned from our mistakes, and have learned to further develop the lighter rocket.