I don't even see the point of checking off an answer lol.
Anyhow. Terminal is like your CMD on Windows. Back in the days, before GUI appeared, people program and work under DOS mode, pretty much plain Terminal. GUI is made to make task simpler and easier, but sometimes using GUI actually requires more work.
For example, as a developer, if I just want to compile a C++ program, I don't have to use sophisticated IDE. IDE is a GUI interface which has many advanced features that a simple text editor does not offer. So instead of downloading a really huge IDE for a simple task, I can just write the following and it will execute my C++ program, whose executable file is called
g++ -o main main.cpp
chmod 777 main
If you do interpreter language like Python, you can enter the Python interactive shell. Yes. There are interactive shells that are wrapped in nice GUI, but it's slower and buggy (oh think of IDLE...)
Sometimes when GUI is broken, you can try to use Terminal to open it. Sometimes, some softwares in Linux don't offer good GUI or it is very difficult to find where the GUI launcher is, you just go to Terminal and type, for example:
This will open the homework.pdf for you.
In another situations, GUI doesn't offer enough power and magic to do your task. Some search functions are very basic, and you can't apply depth-search, or complicated search pattern. But through terminal, a command can be issued with really really complicated and long pattern.
GUI is nice, but sometimes through commands you can make things simpler too. Sometimes you just don't have a choice: you have to use commands through terminals.