Drawables and mipmaps are nearly identical even mipmaps are mostly used for launcher icons and drawables for other things. The suffixes (e.g., -mdpi, -hdpi) are filters,
indicating under what circumstances the images stored in those directories should
be used. Specifically, -ldpi indicates images that should be used on devices with
low-density screens (around 120 dots-per-inch, or “dpi”). The -mdpi suffix indicates resources for medium-density screens (around 160dpi), -hdpi indicates resources for high-density screens (around 240dpi) and so on.
Android Studio offers an Image Asset Wizard. This wizard is designed to take a
starter image and give you icons, in a variety of densities.Android will calculate density of the screen on which app is installed and by that it will take the correct icon. If there is non than Android will take the nearest one. You can find more about mipmaps and drawables on official developer site or any relevant book about android programming like The Busy Coder's Guide to Android Development.
There is Android Asset Studio which you can use in Chrome browser to generate your icons: https://romannurik.github.io/AndroidAssetStudio/