My guesses that you have booted the Mac Mini OK. Yes, you will be able to open all the pre-installed Apple apps; iTunes, Photos, Pages (word processing, which can open and export Word documents), Numbers (spreadsheet, which can also open and export Excel documents), Safari (internet browser), and so on.
If you want to run Microsoft Office using OS X, you can buy and install Office for Mac.
Many other apps have OX S versions available.
If you want to run Windows apps, you need to buy and install Windows. Using Apple's Boot Camp you can run your mac as a Windows computer. If you want to run OS X and Windows at the same time you will need to buy and install Parallels or similar.