Frosch vs. Kröte
The German words Frosch and Kröte both refer to amphibians, but they represent entirely different animals. A Frosch translates to frog, while a Kröte translates to toad. The distinction in German is exactly the same as in English, focusing primarily on the animal's physical characteristics and preferred habitats.
Frosch
The word Frosch translates to frog and refers to amphibians characterized by their smooth, moist skin, long hind legs for leaping, and a strong preference for aquatic or very damp habitats.
Der Frosch springt in den Teich.
(The frog jumps into the pond.)
Ich habe einen grünen Frosch im Garten gesehen.
(I saw a green frog in the garden.)
Frösche brauchen Wasser, um ihre Eier abzulegen.
(Frogs need water to lay their eggs.)
Ein Frosch quakt laut in der Nacht.
(A frog croaks loudly in the night.)
Im Märchen wird der Prinz oft in einen Frosch verwandelt.
(In fairy tales, the prince is often turned into a frog.)
Kröte
The word Kröte translates to toad and describes amphibians that typically have dry, warty or bumpy skin, shorter legs suited for walking or short hops, and tend to live mostly on land.
Die Kröte versteckt sich unter einem großen Stein.
(The toad hides under a large stone.)
Kröten verbringen die meiste Zeit an Land.
(Toads spend most of their time on land.)
Wir haben eine dicke Kröte auf der nassen Straße gefunden.
(We found a fat toad on the wet street.)
Die Haut der Kröte fühlt sich trocken und ledrig an.
(The skin of the toad feels dry and leathery.)
Manche Leute glauben fälschlicherweise, dass man von einer Kröte Warzen bekommt.
(Some people mistakenly believe that you get warts from a toad.)
Summary
In short, use Frosch when talking about a smooth, jumping frog near the water, and use Kröte when referring to a bumpy, terrestrial toad. Both words mirror the exact biological and everyday distinctions found between frogs and toads in English.