Bonnie and CLI!!
One of the things that you will learn in Computer Tech I or Cybersecurity I is that there are myriad operating systems (OSs) in the world besides Microsoft Windows.
One of the most popular OSs is called Linux. Learning Linux is really important, regardless of whether you want to be a software developer (lovingly called a "coder") or you want to work in an Information Technology (IT) shop. Because it is open source ( e.g. free), runs fast, and is quite powerful, Linux is the backbone of many an IT shop. I would estimate that most IT shops run somewhere between 50% - 100% Linux on their servers.
You can download Linux workstation OSs, and server OSs. For example, Ubuntu Linux comes in a standard workstation distribution (called a "distro") and a server version. Moreover, unlike Windows, with just a handful of versions, there are literally hundreds of distros to choose from in the Linux world.
On top of all that, you can choose the kind of "shell" that you want, and the desktop environment you want.
If you are used to the Windows 10 GUI "look and feel" you might want to experiment around with Linux Mint, which looks very similar.
Microsoft Windows is currently offering some choice of shells in today's Windows 10 environment. It used to be that you could (and still can) type in cmd.exe at the run prompt in Windows to bring up the old command window (below left). But today, the command window in Windows has been replaced with PowerShell (below right). However, there is only one desktop environment (e.g. graphical user interface - GUI) that you get with Windows. You cannot change your desktop environment for something that you like better. In the latest versions of Windows Server, you can choose to have no desktop environment at all, and simply live with the Command Line Interface (CLI), or you can install the desktop environment. The Linux CLI is pictured below the Windows command line interfaces.
The Macintosh operating system uses a version of UNIX, called "UNIX Ghost." UNIX has been around for decades and represents a very mature, solid base by which to run applications that must be running nearly 100% of the time. Linux came out of UNIX: an evolution, if you will.
The old style Windows command prompt
The new style PowerShell prompt
A Linux command line interface (CLI)
Boy Howdy, what an Exam!!
CompTIA is not kidding around with their Linux+ exam! This exam is incredibly thorough, and walks you through nearly every aspect of working with the Linux OS.
Why do you need to know Linux? If you are a cybersecurity student, you need to understand that Linux is the backbone of nearly every system that hackers use to devise and launch exploits on another computer or group of computers. If you want to work with servers in some way, you will definitely need to know all about Linux OSs, especially server operating systems (e.g. Ubuntu LAMP).
We do not recommend that you try to go through the Linux+ training first. You should have the CompTIA IT Fundamentals, and A+ certifications under your belt before forging into deeply wooded Linux territory. In fact, it might be wise to consider sitting for the Server+ exam as well.
You can use TestOut Linux Pro for your studies. Linux Pro would not be an altogether bad choice for your studies. You can also use PluralSight and/or Cybrary.IT.
Why would software developers need to know Linux? Well, to be sure, the majority of personal computers in the world predominantly run Microsoft Windows. However, Windows is not the most prevalent OS in the world any longer. In fact, it is Google Android, with some 8 billion installed devices!
The Android OS is a Linux-based OS. You can use Java and Python to program Android computers and phones.