Imagine: You've spent days, nights, and weekends working on a project. While doing the research portion, you created a bib file that you have referenced for all of the writing. Then, on a hot summer day, a thunderstorm hits, and it overloads your surge protector to damage your laptop. You have a few bibliographies in Overleaf, but your hub .bib file is only on your laptop. The file cannot be recovered.
Anything can happen to technology.
We recommend having three copies of anything important: One working copy (on your hard drive or in the cloud), one backup copy (in the cloud or on a physical medium), and one cloud-based copy. You may even want more copies (send a disk to relatives) if it is a very important project, like a dissertation.
Make sure your hub .bib file is located where your backup tool can see it. Dropbox, Box (Yale or otherwise), SpiderOak, Google Drive, and other tools provide user-friendly services for a cloud backup. Here's a comparison list if you're still making a decision, and you can also ask people you know which services they recommend. Do the same thing for physical backup drives.
Consider managing your references in a reference management tool. You'll still need to create a physical backup of your database, which is possible in Zotero, EndNote, RefWorks, and other tools. However, this can make getting back up and running very easy on your new device.
Here are links to some software that will be helpful to you when working in LaTeX. While you can run LaTeX from the command line, many text editors also exist.
Many publishers provide LaTeX templates that include everything you need to get started with citation. Here are links to the documentation.