is no-code, something like using predefined codes?

Sounds like predefined lego like code blocks. If they don't have exactly what you need then you probably have to find someone who can make the block you need. Or pay the company that makes the no-code system.

Using GUI tools which usually require Code to set up.

Also model based development; the idea that the analysis and design of a system is what it takes to implement it, so automating implementation from diagrams is more precise and less error prone than having humans type the code — it's not faster or cheaper as the analysis and design needs to be much more elaborate and complete, but it makes the system more reliable and predictable.

https://n8n.io
is a good example of "no code"

It's like modern day scratch
https://scratch.mit.edu/

Essentially "no code" is a drag / drop gui where you add blocks on to a screen and not write 90% of the underlying code and stick with the core logic and be done in half an hour.