Unity support ships with several inspections designed to help you find issues with your code before you run it. The following pages provide more details about why Rider or ReSharper is showing a particular inspection.
Note that these pages can be navigated to from the Alt+Enter menu, under the "Inspection: …" sub menu, there will be a menu item "Why is Rider suggesting this?" or "Why is ReSharper suggesting this?". Selecting this item will navigate to the appropriate page in the list below.
See also details on performance indicators and the performance critical context.