When you stop your instance, it is powered down at its current state and is available for you to start again at any time. Stopping your instance will release its public IP, so it is recommended that you use static IPs for instances that must retain the same IP after they stop.
When you delete your instance, you are performing a destructive action. Unless you have taken an instance snapshot, all of your instance data will be lost and you cannot recover it again. The instance's public and private IPs will also be released. If you were using a static IP with that instance, the static IP is detached, but remains in your account.