A JAR can either be executable or used as a dynamic link library that's loaded by the JVM at runtime. The JDBC driver JAR is an example of the latter.

No, you don't run the JDBC JAR in this case. You have to package it with your application that accesses Tableau. You need to add that JAR to the application CLASSPATH or package it with your client app.

How do you tell Tableau where to find the JAR and how to configure it? Consult your Tableau docs.