I'd consider basic to be what anyone can figure out just moving sliders around in Lightroom or similar programs. If you need training or extensive research to accomplish it, then it's not basic anymore. So things like adjusting the white balance, contrast, exposure, whites/blacks and highlights/shadows, colour tones and hues, cropping, spot removal, post-crop vignetting, sharpness and noise reduction.
You don't even need to know what any of those things are, you can just fiddle with them blindly and make a reasonable judgment for what looks better or has the effect you want for your image. Obviously an understanding of each feature and experience makes a difference, but I would consider all of what you can fiddle with in Lightroom to be "basic editing".
I'd say other stuff like merging exposures, stacking multiple images, using masks and other things to be more advanced as you need to really learn and perfect those techniques, you can't just stumble upon them and fiddle for a few seconds and end up with anything good.