What is the imperial core?

The "first world". Countries which historically industrialized first, were able to colonize less "developed" countries, and thus have a more or less stable economic advantage in terms of dictating an unequal trade regime. This is the true reason wages and cost of living are lower in the "developing" world. These countries were basically opened up to international trade at gunpoint, forced to rapidly industrialize, and forced into being a source of cheap labor and resources for the imperial core.

i recommend this video on the broader subject of imperialism

or this one to a lesser extent

Does this mean things like mining lithium, or exporting labor to other countries because it's cheaper?

yes

Sorry if these questions sound dumb.

there are no dumb questions