In STM32 microcontrollers there is a distinction between HSI and HSE(high speed external). This indicates an internal external distinction.
On the other hand as shown in this document there is external clock-source concept as ETR:
Also here it says:
Timers get their clock source from External pins or Internal timer sources.
So it seems there is two types or internal external distinction or am I interpreting something wrong here?
Is HSE and ETR same things? Or HSE is a subset of internal clock source?