Minecraft wiki entry for Healing, associated text: Both golden apples refill 4 () hunger.
They provide 9.6 saturation, which can be drained for 6 quickly if the player's hunger bar is filled.
Similar to a potion, a golden apple provides the Regeneration status effect. A normal golden apple gives Regeneration II for 5 seconds, and an enchanted golden apple for 20 seconds, resulting in 4 regenerated from a normal golden apple and 16 × 8 from an enchanted one. In Bedrock Edition, enchanted apple gives regeneration V for 30 seconds, which enough to recover full health in a few seconds. The enchanted golden apple also gives the status effects Fire Resistance and Resistance for 5 minutes.
A normal golden apple can be crafted by 8 gold ingots, and a regular apple, and can be found in generated chests. The enchanted golden apple cannot be crafted, and are found exclusively in generated chests.