Applications are the tools people use to do useful things with computers, such as word processing, spreadsheets, presentations, databases etc.
Office
In some areas these applications are dominated by a single program, which – due to its dominance in that area benefits from a feedback loop – since it is so widely used – is the only one which is taught, and hence the only option people know of.
This does not result in a healthy marketplace.
For the Microsoft Desktop Applications there are alternatives which perform the same functions, and trying out these alternatives improve understanding of the application, and even make transition from, for example one version of Word to the next easier.
Following the overall approach of small actionable steps, installing LibreOffice alongside Microsoft Office (if you use it), does not prevent you from using Word to process documents, but allows you to try an alternative. If you have an old PC you might try installing LibreOffice on that.
Security
As the number of services we use increases the number of passwords we should be using increases. Since some services are much better protected than others, if you use the username and password you use for your bank to, for example, enter a competition you have seen on the internet, then you could be making an expensive mistake.
An old fashioned solution is to use a paper notebook, but people are not good at inventing passwords on the spur of the moment and a Password Manager is a better solution. If possible, and not all systems allow this, making user names different with Plus Addressing is a good additional security measure.
Web Browsers
Chrome, the browser produced by Google, is very good, freely available, and handles the complexities of the modern web very well. Due to its omplexity and market dominance it is a tempting target for security vulnerabilities. Creators of web applications also become lazy and only test on Chrome, creating pages which do not work with other browsers. If you use some other browser, such as Firefox first, and the site does not work with that, it is a sign that the sites is poorly designed, and you may want to find an alternative. You should also let them know (if you can) that they have a problem