Headings provide a hierarchical structure for the content and communicate the relationship between different pieces of content. They indicate which information is most important and which content is a subset of another.
Visual indicators such as colour, size, and orientation help communicate that structure to those without visual impairment, but a screen reader has to use the heading levels to provide the structure.
It is therefore very important that you make sure your headings are ‘nested’ in numerical order, eg. heading 2, heading 3, heading 4.