Tables
Tables need to have column headers and/or row headers. Table Headers are different from the Headings you use for section titles. So, you can’t simply reformat the text as a heading, you will need to tag the cell as a header. In many apps, checking the header box or marking the cell as a header will do all the formatting for you, saving you a lot of time. Using column/row headers also allows those using assistive technology to know where they are at in the table.
Without these headers, the table is read from left to right, top to bottom. There is generally no identification to which column you might be in. (Think of a linear list of data). When headers are used, the user is notified what row they are in, what column, the name of the column, and then the information that is in that cell. The formatting that might be taken in visually gets read out properly to those with visual impairments.