Icons have different accessibility requirements dependent on the context they are being used in.
Icons by default are presentational only meaning they do not provide any context to screen readers and will be purely cosmetic without additional markup.
When icons are used in buttons or links they should be used in conjunction with descriptive text.
If the icon in an interactive item does not have text then the parent interactive
item (typically a button or link) should have an appropriate aria-label
describing the interaction.
If an icon is used to show a status/indicator or part of a larger body of text then the icon should have a title attribute so the icon can be properly read by the screen reader.