A RAID is essentially a way to have multiple "hard drives" connected in a way that looks as if it's one drive so you can have a ton of storage.

A NAS is a sort of like a remote storage device. Not quite a PC, but more than just a storage drive.

Not sure how you'd go about doing any of that with a MacBook.

NAS stands for "Network Attached Storage", basically a computer whose sole purpose is storing and serving files in your home.

RAID stands for "Reduntant Array of Inexpensive Disks", and is broadly a way to merge multiple disks into one.
RAID 0 means that files are evenly distributed on all disks, which improves IO speed and extends a file system (≈ a partition) 's capacity, but it's useless against disk failure;
RAID 1(mirroring) means that all disks have the same data as a sort of real-time backup, and as long as one disk remains functional, all the other disks can fail without the data becoming inaccessible;
other RAID levels use clever math to offer a mix of the first two, spreading files among disks (like RAID 0) but still tolerating failures of a small number of disks (like RAID 1 but way less redundant).

Wikipedia has a less abridged explaination on its RAID page.

A piece of advice with ZFS, get the largest drives you can afford.

Expanding ZFS is painful and it's wayyyyy easier to just start big then to grow big.

ZFS is also a RAM hog, max out your ram cause that.

If you want to add meta data caches, do it when you first build the array.

The L2-arc cache and SLOG don't do what you think they will. Make sure you really understand them before you throw them on. They're easy to take off though.

Last but certainly not least, ZFS is a money sink. It was made for enterprise solutions, meaning it benefits from more money being thrown at it than say XFS. Figure out what's good enough and live with it.

I switched to raid z2 from a 6 drive mirror and what an ordeal that was. It's because I had to grow into it and buy drives over time but eventually the mirror was too inefficient.

I moved data around like 5 times all because I still didn't have enough disks to build my new array and keep my data on the system at the same time. And expanding raidz expands parity on all disks but not the data so you have to recopy all your data so it stripes fully.

I had a backup on a DAS but USB is slow and I didn't want to have it be the only copy.

Edit: clarifying my point. I have no regrets. ZFS is awesome. But make the important decisions up front and yes start with the right amount of drives that you need. My whole issue was growing into it and having to make changes after the fact.