How do I uninstall certain applications "required by Mac OS X".

To uninstall any app, just drag it to the Trash, or right-click and "Move to Trash". That is usually sufficient to uninstall the app. However, most apps leave files/folders behind, such as preference lists, caches, etc. These have no effect on your system, other than taking up drive space. If you want to get rid of all traces of an app, the most effective method for complete app removal is manual deletion:

Best way to FULLY DELETE a program​

However, be careful about deleting apps that came pre-installed on your Mac. You may find you need or want some of those later. Your user files will take up more space on disk than having apps installed, so it's better to leave pre-installed apps alone.

Installing Applications in Mac OS X
Uninstalling Applications in Mac OS X

 

I don't think you can get rid of those applications, they're common to every mac. As for your second question, where are you installing them? Are you dragging the download to the applications folder?

 

Are you actually installing the applications or are you just mounting a DMG and running the applications from there? I'm confused on why they are listed under devices.

 

What you are doing is downloading a dmg file and that opens in your devices and acts like a drive. You have to either use an installer located in that dmg or drag and drop the application into you applications folder.

In the firefox example it gives you an alias to your applications folder inside so all you have to do is drag ff to that application folder icon and it will copy it to your computer. Now you can eject the dmg from your devices and trash the file you downloaded. Firefox is now installed in your applications folder.

 

AFAIK, these applications can be removed. However, they should not be removed. It is true that they are common to every Mac. However, they are also common to every user on the Mac. Because they are common to every user, Apple gives applications like Mail and Safari system administration functions. Mail sets the default email client for the user. Other email clients may have this function if the developer chooses to support it. The second most popular email client on MacOS X is Mozilla's Thunderbird. Thunderbird cannot set your default email client. If you had adopted Thunderbird and deleted Mail in the false confidence that Thunderbird can do everything that Mail can do, then you would have been in for a surprise.

 

Thanks for clearing that up MisterMe.