In the course of civil litigation, it is not uncommon for parties to settle out-of-court prior to - or even during - a trial.
In cases where there are multiple defendants, there may be situations in which some defendants settle out-of-court and others don't. While those that do settle may not longer be compelled to pay additional damages, they may still be found liable in court. Generally what this means is that damages owed by the remaining defendants will be reduced by whatever share the settling defendant would have owed.
However, there is the issue of joint and several liability. This is when there are multiple parties liable for the same act or event, and plaintiff could collect damages from any, several or all liable parties.