QA, or quality assurance, is a common practice in the final stages of the digital product building process.
At this stage, QA engineers typically test each of the features that have been implemented and verify that they are working properly and within expectations. If they encounter a bug, they usually forward it to the development team (if it is a frontend or backend implementation technical problem) or design (if it is a visual, writing, or browsing issue).
It is as if at this stage you passed a fine comb through the product, to check for problems from both a creative and technical point of view.
The problem is: QA engineers are not always trained professionals to check the quality of the user experience. Not because they are incapacitated professionals—far from it—but because this type of verification requires a broader understanding of the context in which experience takes place.