What does

*

mean?

That indicates your currently selected stack. If you run

pulumi stack select dev

, you will see the asterisk appearing after

dev

.

staging

and

dev

both have a pink row in the website but only

dev

has a

yml

file. Is this wrong?

Not necessarily. My assumption for now is you have set stack configuration values on

dev

, but not yet on

staging

. Am I right on this?

I haven't really worked out what the yml files do yet

The yaml files represent the config for each of the stacks you set up using your Pulumi project. I suggest you give the stack documentation another read: https://www.pulumi.com/docs/intro/concepts/stack/

So to create a new stack I need to use the command line command and then create a new

yml

file?

To create a new stack, you only run

pulumi stack init

, you don't have to create a yaml file yourself. If you set any stack configuration using

pulumi config set

afterwards, Pulumi will create the yml file for your stack when it doesn't exist.