Locally running OpenMRS ESM Template App and backend

Dear Team, I am new to OpenMRS 3 and trying to learn by following Intro to OpenMRS 3: For Developers and Technical Teams In below video , https://openmrs.org/academy/intro-to-openmrs-3/lesson/o3-frontend-development-live-coding-session-hello-world-in-10-mins/ I ran OpenMRS ESM Template App locally (not used gitpod) cloned the repository and cd to it then yarn and yarn start and i can open the app in browser http://localhost:8080/openmrs/spa/home# Now question is where and by which command the openmrs back-end is running ? little bit confused as i also watched other videos like setting up O3 with Docker and SDK and here i see that no need for setup. I am sure that i am missing some basic fundamental here, any hint reference to understand same? I also see in some videos , regarding Implementer tool by which we can do changes using same and could load the config to apply it to persist. What are the use-case of these two scenarios Implementer Tools and through “OpenMRS ESM Template App” way? One last question, when we run O3 by using GitHub - openmrs/openmrs-distro-referenceapplication: The reference distribution of the OpenMRS EMR application (v3) , which repository it uses to build frontend ? is OpenMRS ESM Template ?

Thanks in advance