The Resistance was a rebellion movement that was led by Leia Organa in the Star Wars franchise.
The Resistance was formed about three decades after the Battle of Endor by Princess Leia Organa after she felt the New Republic was not doing enough to counter the threat of the First Order. She was able to convince many of the military personnel who had been sidelined by the New Republic's disarmament act to join her along with others in the New Republic who realized the threat of the First Order.
The Resistance was able to secure funding and equipment from sympathetic individuals in the New Republic Senate. These included T-70 X-wing starfighters which were more advanced than the T-65 X-wings used by the Rebel Alliance.
The Resistance adopted an insignia used by the Rebel Alliance. Leia Organa became the main leader of the group, adopting the title of General. Admiral Ackbar was another important Resistance leader. The Resistance adopted the the Rebel Alliance's symbol. They first made their headquaters on D'Qar. The headquarters served as the command center for the X-wings. Their military forces were known to fight the First Order with hit and run methods.
After the Starkiller superweapon destroyed the New Republic's capital in the Hosnian system the Resistance staged an attack led by Han Solo, Rey, Chewbacca, Finn, and Poe Dameron. Solo and his companions were able to disable the shielding, and Dameron was able to destroy a vital conduit with his fighter, causing the weapon to explode.
After the Starkiller weapon was destroyed the First Order begin to take over the galaxy and almost drive the Resistance into extinction by destroying their base and left the remaining survivors fleeing in the Millenium Falcon.