Frogs are amphibians found in both wizarding and Muggle areas.
Ron has a big one in a tank in his bedroom at the Burrow (was filled with frog spawn before) (GF5). They also live in the Weasleys’ garden pond (CS3). Frogs are used in potion-making (CS8).
Frogs have been associated with witches since people of the Middle Ages believed the amphibians to be one of the creatures commonly used as familiars.
The witches in Macbeth by William Shakespeare use frog toe (along with parts from other creatures long associated with magic and the occult, including other amphibians and sundry reptiles) in their potion.
source: Macbeth IV.i