Smart previews
Smart previews are light, compact copies of your RAW files that Lightroom Classic can create. They let you edit photos while the originals aren't connected, for example when they're on an external drive. When you reconnect, your changes are applied to the originals automatically.
Ideal if you keep your archive on an external drive but want to keep working on your laptop on the go. Smart previews are smaller than the original, so they take little space yet are large enough to edit well. Your catalog stays nicely workable without every drive connected. Tip: build smart previews on import if you work a lot with an external drive and laptop.
Related terms
Prefer a look in one click?
The presets on this site set these adjustments up for you as a starting point, which you then fine-tune to taste.