How to apply the different parts of Grafana

I’m sorry, I feel ignorant, but I don’t understand what the use is of and how to use different parts of Grafana.
First of all: what is the use of creating a Grafana account? What does that enable me to do?
Secondly: what is the use of installing local Grafana server software? Do I need that to create dashboards (on the internet)?

Kind regards,
Jurgen Runge