A froglet is a young frog that has just finished metamorphosis, the change from a water-dwelling tadpole into a frog. In the common frog, tadpoles grow back legs and then front legs, absorb their tails, and leave the pond as tiny froglets, usually in early to late summer.
Froglets look like miniature adults and live on land, where they feed and grow before spending their first winter in hibernation. They are not yet able to breed: common frogs reach breeding age at about two to three years old. A young toad at the same stage is called a toadlet.
Source: Froglife: Common Frog
Image: A froglet at Gordon Moss Nature Reserve, by Walter Baxter, CC BY-SA 2.0, via Wikimedia Commons.