Gnucash opens and saves a file containing all your data in the same way as text softwares such as Microsoft Word or LibreOffice.
You can have multiple totally independent gnucash files, one for your personal accounting, one for your small business. Each file contains its own gnucash accounts
, etc.. So you have all the freedom to do your accounts in a single file to create one file per year, fiscal period, and so on.
It also allows you to save all your accounts in one step by copying the file on a USB stick or CD for security reasons.