Short answers, pulled from the story.
The Civic Crown (corona civica) was a military decoration given to Roman citizens who saved the lives of fellow citizens by killing an enemy in battle. It took the form of a chaplet of common oak leaves woven into a crown. It was ranked as the second-highest decoration a Roman citizen could receive, behind only the Grass Crown.
Only Roman citizens who killed an enemy soldier while saving the life of a fellow citizen in battle could receive the Civic Crown. The person whose life was saved had to personally confirm the act; no other witness was accepted.
After Sulla's constitutional reforms, recipients of the Civic Crown were entitled to enter the Roman Senate. By law they were required to wear the crown at every public gathering, and the senate would rise when they entered the games. The recipient, his father, and his paternal grandfather were all exempted from public duties.
Julius Caesar was awarded the Civic Crown for his service during the Siege of Mytilene in 81 BC.
Siccius Dentatus won fourteen Civic Crowns, the highest number recorded. Marcus Capitolinus won six, one of which was awarded for saving the life of his commanding officer Servilius.
Scipio Africanus refused to accept a Civic Crown for rescuing his father at the Battle of the Trebbia. Pliny records the refusal in his Naturalis Historia without criticism, presenting it as consistent with a character that sought no reward for doing what duty required.