Your photos are now in Lightroom and you want to sort and edit them. You go from photo to photo and there is a small delay while Lightroom is generating the preview. It can get long and boring and you lose a lot of time doing it this way.
So after importing, ask Lightroom to generate the 1:1 Previews. You can do that on import but I usually do that just when I'm ready to edit this session.
Go to the Library menu, under Previews, click on the Build 1:1 Previews. It takes some time to do that so do it before going to sleep or click it and get a lunch or coffee. When you come back though, you can zoom in on photos, check if they are sharp, etc., and it is instant. No more waiting for Lightroom to generate the preview. It may takes some time and disk space but the editing process is a lot faster after that.
To prevent your Lightroom Catalog from becoming a huge beast that eats your disk drives, go to the Catalog Settings and set the Automatically Discard 1:1 Previews option to what is good for you. The best option depends on the volume of work you have and the time it takes you to edit your files.