Rana vs. rospo
In Italian, the words rana and rospo both refer to tailless amphibians, but they are not interchangeable. While rana refers to a frog, rospo refers to a toad. They also carry very different figurative meanings in everyday language.
Rana
The word rana translates to frog in English. It refers to the smooth-skinned, aquatic or semi-aquatic amphibian known for jumping, and is also used to describe the breaststroke swimming style.
I bambini cercavano di catturare una rana vicino allo stagno.
(The children were trying to catch a frog near the pond.)
Ho ordinato un piatto tradizionale a base di cosce di rana.
(I ordered a traditional dish made of frog legs.)
In piscina preferisco nuotare a rana piuttosto che a stile libero.
(At the pool I prefer to swim breaststroke rather than freestyle.)
La rana verde saltò improvvisamente nell'acqua fresca.
(The green frog suddenly jumped into the fresh water.)
Molte fiabe iniziano con una principessa e una rana incantata.
(Many fairy tales begin with a princess and an enchanted frog.)
Rospo
The word rospo translates to toad in English, referring to the warty, terrestrial amphibian. Figuratively, rospo is often used to describe an ugly or grumpy person, and in idioms it represents swallowing a bitter pill.
Durante la passeggiata nel bosco abbiamo visto un grosso rospo sotto le foglie.
(During the walk in the woods we saw a big toad under the leaves.)
Non fare il rospo e cerca di sorridere un po' di più alla festa.
(Do not be a grump and try to smile a bit more at the party.)
Purtroppo ho dovuto ingoiare il rospo e accettare la sua decisione ingiusta.
(Unfortunately I had to swallow the bitter pill and accept his unfair decision.)
La strega cattiva trasformò il bellissimo principe in un rospo.
(The wicked witch transformed the beautiful prince into a toad.)
Il rospo ha la pelle ruvida e vive principalmente sulla terraferma.
(The toad has rough skin and lives mostly on dry land.)
Summary
To summarize, use rana when talking about a frog or the breaststroke swimming style. Use rospo when referring to a toad, an ugly or grumpy person, or when expressing the need to accept a difficult situation through popular idioms.