Help me learn what this is- what to learn?

I once had to combine an absurd amount of csv files that it wasn't feasible for me to use an online service nor to manually join/append them using excel/Gsheets, and I looked for a solutions online and one was with three simple commands using the terminal -granted all these csvs were the same structure-, and viola! they were combined in seconds.

The other time is where I had almost 700 broken music files in a folder and I needed them in a csv sheet so I can look for them easily, again, I looked for a solution and it was a 1-command in the terminal, and a csv file with their name was created.

These instances showed me that our devices are already capable of doing so much stuff that we don't need all those paid online of offline software solutions, the only problem is, I don't know what domain of knowledge is that?

Can you please tell me what should I learn to master this?

is this shell/bash/zhs something else?