What is the difference between being redeemed and being saved?
The short answer
Redemption is collective; salvation is individual. Christ redeemed the whole human race from slavery to sin and its debt of punishment, so every person is redeemed. Salvation is that redemption applied to an individual — and a person can reject the graces Christ won for him.
Redemption: for all
Christ redeemed humanity as a whole from slavery to sin and from the debt of punishment the human race owed because of sin. Every person, Christian or not, is redeemed simply by belonging to the human race.
Salvation: for each person
Salvation is the application of that redemption to individuals. Even though someone has been redeemed, he can choose to reject the graces Christ won for him.