Why it matters
Icon-only buttons without a label are announced as just "button", so screen-reader users cannot tell what they do.
How to fix it
Give the button visible text, aria-label, or visually-hidden text.
Example
<button aria-label="Close dialog"><svg aria-hidden="true">…</svg></button>References
More accessibility rules
void a11y reports 48 rules in this category. WCAG 2.2 AA through axe-core, plus checks axe can't do alone: visible keyboard focus, 24/44px target size on mobile, 320px reflow and disabled zoom.
color-contrastText has insufficient color contrastimage-altImage has no text alternativelink-nameLink has no accessible namelabelForm field has no labelselect-nameSelect element has no accessible nameinput-button-nameInput button has no accessible nameinput-image-altImage button has no alt texthtml-has-lang<html> has no lang attribute