Raw card vs. graded card
"Raw" is the hobby term for an ungraded card: exactly as it came out of the pack or set, with no outside company having evaluated its condition. Most cards in circulation are Raw.
A "graded" card has gone through a specialized company (PSA, BGS and SGC are the best known) that reviews it, authenticates it as genuine, and seals it inside a rigid, transparent case ('slab') with a label showing the grade.
How the grade works
PSA and SGC use a 1-to-10 scale, where 10 is 'Gem Mint' (essentially flawless). BGS uses the same scale but can also show four sub-grades (centering, corners, edges, surface) that combine into the final grade.
The grade is based on four physical criteria: how well the image is centered relative to the border, corner condition, edge condition, and how clean the surface is (no scratches, fingerprints or stains).
A single point of difference (e.g. PSA 9 vs. PSA 10) can mean a huge price difference on the market, especially for popular players or heavily limited print runs.
Is it worth paying more for a graded card?
Grading provides two things a Raw card can't guarantee on its own: certified authenticity (confirms it's not a fake) and an objective condition verified by a third party, not just the seller's word.
That's why a graded card usually sells for more than the same card Raw, even in good condition: the buyer is paying for certainty, not just physical condition.
For entry-level pieces or hobby collecting, a Raw card in good shape is perfectly fine. Grading makes more sense for higher-value pieces, autographs, or very limited print runs.