Question: In AEM speak - what is the exact conceptual difference between between currentstyle and currentdesign objects available after including the tag in template / component?

Answer: 
Just to add some clarify to what's already here:

Global content (that is, component values that are common across multiple instances of the same template) are stored as "styles" and edited via a "design dialog".

They are stored as follows:

```
/etc/designs/<design>/jcr:content/<template>/<component>

```

So, for the component `logo` in the template `homepage`, using the `default` design:

* `currentStyle` is `/etc/designs/default/jcr:content/homepage/logo`
* `currentDesign` is `/etc/designs/default`
I would say it is more like:
`/etc/designs/<design>/jcr:content/<resource-type-of-page>/<component>`
so that different templates having the same page resource type will share the same style