Non-destructive editing
Non-destructive editing means your adjustments are stored separately from your original file, so your original pixels never change. Lightroom works this way by nature: it only saves instructions, not a new file. So you can always return to the start.
The big advantage is freedom: you can slide, undo and experiment endlessly without quality loss. In Photoshop you work non-destructively by using adjustment layers, smart objects and layer masks instead of editing pixels directly. Save your Photoshop file as PSD or TIFF to keep those layers. It costs a bit more disk space, but your future self will thank you when you want to tweak an edit.
Related terms
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The presets on this site set these adjustments up for you as a starting point, which you then fine-tune to taste.