You GP most likely searches WebMD... general practitioners and internal medicine is pretty much knowing what to search for no human can have all that knowledge in their head readily accessible.

For example when a doctor asks you if you travelled recently they aren’t going to know which contagious diseases are local to where you visit. So if you tell them you went to Belize they’ll open https://wwwnc.cdc.gov/travel/destinations/traveler/none/beli... and see if anything there matches your symptoms.

For surgeons it’s mostly practice, practice and practice on how to cut you up and stitch you back together in the cleanest and fastest way possible.