This article was written using LibreOffice's Writer, an open source alternative to Microsoft's Word. There are multiple free options, software that you can download and use for no charge, that is comparable to the paid software that everybody is used to, like the Microsoft Office suite (Word, Excel, PowerPoint).
Here's a short list of free and/or open source software that are worth a try:
Gimp or GimpShop, as alternatives to Adobe Photoshop
FreeCAD, a free alternative to AutoCAD
VLC, a video player that outclasses Windows Media Player and successfully replaces QuickTime
7-Zip, free alternative to WinZip and/or WinRAR
IrfanView or Picasa - free picture viewer, editor, manager, that covers a large number of picture formats
… and others
Many of us are so used to one software or the other, or we are simply unwilling to experiment with new software. Software companies realized that it is profitable to offer their software as a service, where you get to use their products for a limited period of time, essentially renting it, paying to use the software for a limited time. This is a useful alternative if you are running small projects, that require the use of a certain software, where you don't intend to buy a full license.
Here are a few ideas: Adobe Creative Cloud, Microsoft 365, IBM Cloud Computing, Google Apps, Salesforce.com
Beware of scammers!
When buying software, you should never accept an “open box”, or a software without the accompanying license (product) key, that is always included in a sealed envelope or box.
Most software can be nowadays bought and downloaded directly from the company that produces it; avoid being the victim of software scammers. Ask for a second opinion when things don't seem right.
Do you have your own favorite open source software? Do share.