Need Help with Registry 'Language' and more!

I am not well-versed on my household necessities and reading over registry checklists and information I find myself questioning a few things. Here are my questions for you registry know-it-alls out there:

1. When they say '5 piece place setting' which 5 pieces are they referring to exactly?

2. What are 'china savers' and are they necessary?

3. Is it OK to register for a vacuum, etiquette-wise?

4. What is a 'completer set'?

5. I want to order a set of dishes for entertaining and a set of dishes for everyday use. Is it recommended to order different glasses as well?

6. Will I need a cleaver and a boning knife?

7. When it comes to flatware, what is a 'hostess set' and what is a 'serving set'?

Okay I think that's all for now. Thanks in advance for your help.

1. When they say '5 piece place setting' which 5 pieces are they referring to exactly?
***Dinner plate, appetizer plate, dessert plate, coffee or tea cup and saucer

2. What are 'china savers' and are they necessary?
***Not necessary, but a good idea. They're storage units designed specifically for fine china.

3. Is it OK to register for a vacuum, etiquette-wise?
***YES!

4. What is a 'completer set'?
***a set of supplementary pieces that completes a set of dishes, as creamer, sugar bowl, platter, gravy boat, and vegetable dish.

5. I want to order a set of dishes for entertaining and a set of dishes for everyday use. Is it recommended to order different glasses as well?
***I would

6. Will I need a cleaver and a boning knife?
***Eh, maybe not......but put it on, you can always return it

7. When it comes to flatware, what is a 'hostess set' and what is a 'serving set'?
***Generally a serving set is 3 pieces and has your cold meat fork, gravy ladle, and cake/pastry server. A hostess set has 4 pieces and includes your serving spoon, slotted serving spoon, butter knife, and sugar spoon. And yes, you need both sets.

THANK YOU!!

So for the dishes, if bowls are not included in the 5 piece set, is it usually hard to find matching bowls to go with it?