We have discussed previously how Heroku uses a dyno model so you do not need to deal with all the complexities of a server. A dyno is a container that runs a single application processes. The process types are defined in a simple text file called Procfile in the root of your project.
There are two process types you can define: web and anything else.
A web process listens to requests and responds with results, just as a web server or application server would.
All request sent to your application are routed through to the dyno's you have running. So the more dynos you run, the more requests you application can process.
Worker- a generic name for a background task.
Queue- a process that consumes data from a queue service attached to the application. Typically data is passed to the queue from a web process, so that process does not have to perform any long operation or extended wait.