When you right-click a file in Finder and select “Open With…,” a list of applications is shown. However, if you’re installing and uninstalling applications, this list can become a bit muddled with apps you don’t even have anymore.
By rebuilding the Launch Services Database, you fix these default app associations, check and restore file icons, and solve other app-related issues.
When your Mac accesses a website for the first time, it basically asks, “Hey, what’s the IP address for [website]?” The DNS (or Domain Name System) maps website names to IP addresses. For example, blog.macpaw.com to 22.214.171.124.
The memory of all these names and IP addresses is called the DNS Cache. Sometimes this cache becomes corrupt or out of date, resulting in you not being able to access a website. Flushing the DNS Cache can resolve this issue and others.