I want to say i am not an expert at this field but i know a bit about this topic and with some research have compiled a bit of information regarding your question. To start off, cpp (c++) is usually used in fields requiring high performance, low latency, and direct hardware control.
Some typical uses:
- OSs ( Operating Systems )
- Gamedevelopment, for high performance and physics heavy games for example in Unreal Engine
- Embedded System and IoT (Internet of Things ): for automotive systems and IoT gadgets and medical devices
- Browser development and Databases
- Science-Physics Simulations ( AI too but for AI development is python the go-to language )
- Compilers & Libraries: For example the Java compiler is written in Cpp
I hope this will help you a little, some resources to get better at cpp for free are
https://www.w3schools.com/cpp/ and i personally would recommend the youtuber BroCode, here his cpp playlist
https://www.youtube.com/watch?v=S3nx34WFXjI&list=PLZPZq0r_RZOMHoXIcxze_lP97j2Ase2on&index=1