Since you are a first time cruiser I'll agree with cnmiranda but go into a little more detail.
What is in effect now on all NCL ships except POA is an 'automatic' $10 pp/pd charge. This is automatically added to your bill but can be removed if you go to the desk and say you do not want to give that amount of tip.
The new service charge will also be added to your account but cannot be removed or adjusted in any way. Thus it switches from being just 'automatic' to being 'automatic' and 'mandatory'.