The Theme settings control your general settings of the theme. Theme settings control specific elements to the theme that are not limited to sections. For example, Typography controls the font for all elements specified on the storefront.
Your store’s general settings control global adjustments which affect your entire storefront rather than for example, the sections settings which are isolated to each individual section.
Shopify has a great help guide relating to this here:
To find your general settings, head to:
Online store → Themes → Customise
Your general settings area features a large number of options, displayed here:
Each of these sections is described more fully in our help documents linked to on the right-hand side of this page.