What is iCloud Drive and should I use it? For what?

There is no requirement to use it.

If you have an iPhone or iPad, you can go to Settings > [username] > iCloud and see what, if any, iCloud options are turned on.

I do use it for iCloud Photos (I have a small photo library of about 1,000 photos) and I also sync Contacts and Notes and I use iCloud Backup for my iPhone. All of that fits in the free 5GB so I am not paying for anything and if my phone is lost or damaged I won't lose my photos, contacts or notes. If you want to see how much, if any, storage you are using, see instructions in: Manage your iCloud storage - Apple Support

iCloud Drive is primarily a way of syncing your data files between devices. See the iCloud Drive section of https://www.apple.com/icloud/ and also see: iCloud Drive FAQ - Apple Support

Using macbook pro. Here is an example of my problem. I received 3 pdfs in gmail from insurance co. I need to save them all for my records. One needs to be signed and returned. They each offer two ways to save - pdf and Drive.

Only one saved to my desktop, as a pdf. The other 2 disappeared. I assume they went to DRIVE altho I clicked pdf. (and then, when desperate, clicked drive). Disappeared!!!

DRIVE, NOW, is something new to me. For a few years it showed up and I could always find the documents, but not anymore. Since I've updated the OS I can't find anything. It is like learning computers all over again. (I do not want to have to learn a bunch of new stuff every six months. I just want to get my basic work done and then read a good book). I see

Drive is in google (or iCloud) . I just recently quit using google - except for email and searches - and am using Safari. Safari seems to NOT work with many things. Like TURBO TAX.

I really do NOT need or want to have everything on ALL my devices. I use them for different things and like to keep the info' separate.

So now opening a pdf which used to be fairly easy is now a nightmare and mystery. And how in the world do people do business anymore without a computer????

What if I do not use iCloud?\So far, I am not aware of using iCloud and have avoided any efforts to sign up with it. I do not intend to pay for expensive subscription to iCloud

PLUS! I changed to Safari because APPLE recommends using SAFARI!! although it seems not to be compatible with so many things, such as pdfs! or Drive! And Turbo Tax!!!