All tyres have reinforcing cords or 'plies' under the tread. A radial tyre is so-called because the plies run radially (ie from one sidewall, across the tread, to the other sidewall). This is different to a cross-ply or bias-ply tyre.

Radial tyres are universal on modern cars, because they offer the best combination of grip, handling, ride and tyre life.