What is "anecdotal data" and how does it differ from non-anecdotal data? How do data collection methods on something like micro-aggressions ensure no low quali

What is "anecdotal data" and how does it differ from non-anecdotal data? How do data collection methods on something like micro-aggressions ensure no low quality "anecdotal data" gets in? It would be more defensible to claim anecdotes were lower quality evidence than "data" (assuming such a distinction were clear, which I'm not sure it is) than to claim they simply aren't evidence.