The five categories collectors recognize
Miscut
The cutting blade misaligned, leaving a sliver of an adjacent card or the print sheet outer margin visible. Severe miscuts, where the adjacent card artwork is clearly visible, trade for real premiums. Mild miscuts (a few millimeters of border imbalance) do not.
Missing color or missing ink
A printing plate failed mid-run, leaving a card with a missing color layer. A Charizard with no orange ink, a holo with no foil layer, an HP value printed but the HP digit missing. These are scarce and command premiums when authentic, but they need to be definitively from the factory and not from physical wear.
Stamp misalignment (1st Edition era)
The 1st Edition stamp printed in the wrong place under the artwork. Off-center stamps, double stamps, and inverted stamps exist. The "no stamp" variant of an otherwise-1st-Edition card is famously valuable on a few cards, notably the Jungle No Symbol error.
Holo bleed and ghost holo
Foil pattern that extends beyond the artwork window, or a faint foil ghost of the holo pattern bleeding into adjacent non-holo areas. These are cosmetic, not scarce. They will not lift the price of a common card meaningfully.
Reverse holo on a non-reverse position
A reverse-holo finish accidentally applied to a card position that should have been standard. Modern booster boxes occasionally produce these. They trade at small premiums in graded condition.
The famous ones
The No Symbol Jungle error. The first print of Jungle accidentally shipped without the set symbol in the lower-right corner of every card. Wizards corrected the symbol on the next print. Both versions are 1st Edition; the No Symbol cards trade at a meaningful premium across the set.
The "Edition 1" misprint on Neo Discovery. A small batch was printed with the stamp visible inside the artwork window instead of below it. These trade in the four figures for marquee cards.
The Charizard ghost holo. A small Base Set Unlimited print produced cards where the holo pattern bled lightly across the artwork. Some buyers treat these as defects; others as genuine errors and pay accordingly.
How to value an error
There is no general "error premium." Each famous error trades on its own population and demand curve. For a one-off miscut or missing color, you are pricing a 1-of-1 oddity, which means the value is whatever the next buyer will pay. Use sold-comp searches on TCGPlayer, eBay, and PWCC auction archive to see if the specific error pattern has changed hands recently. Without comps, treat the price as a guess.