There are many different file-storing, file-syncing, file-backup options out there, but in my mind none are as intuitive, complete, or reliable as DropBox.
This is a quickly evolving space, file-management, but DropBox has been a reliable and consistent player for many years. It could be argued, in fact, that they were the first major player outside of the corporate beasts (Google, Amazon, Apple, Microsoft) who otherwise dominate such spaces.
What I like about DropBox is that I don’t have to think about it. I have a drive on my computer that is my DropBox drive, and anything I want backed up goes in there. As a result, I essentially have my apps and temporary files just on my computer, while the important files and documents, along with my auto-backed-up media like photos and videos, are in the DropBox drive. This drive syncs with the cloud (so if my computer is stolen or broken or dropped into the ocean, my files are safe) and with my other devices, so I have access to the same files regardless of which hardware I’m using.
When I take a photo on my iPhone, it auto-uploads to DropBox, so I have access to it on my Android phone, on my computer, on the web; the convenience of this cannot be overstated.
We also use DropBox to organize our files for Asymmetrical Press. Our books, our logos, our promotional materials, are available to everyone who has access to the shared Asymmetrical folder. Outside of that, I have my own private folders, where my photos and whatnot are shared between my devices. I can also share any of these private folders or files any time I like, giving viewing or editing rights to whomever I like.
I pay about $100/year for DropBox Pro (1 TB of space and some other little benefits), though some people will get by just the Basic account (2 GB of space for free), and others will need a DropBox Business account (unlimited space, file recovery, and some additional collaboration tools).
Again, this is a quickly evolving space, and a lot of the other services offer the same or similar things, and even some options that DropBox doesn’t, or at least not as well (Google Drive syncs up nicely with other Google services, like Docs, for instance, which allows for the online editing of Word docs and spreadsheets).
Sort out your needs and take a look at all of these cloud services’ offerings, maybe try them out for a few weeks, before committing to one of them. Then double-down on that one and enjoy the benefits of hardware agnosticism, your files safe and happy and accessible wherever you want them.