Whats the difference ?

I would like to know the difference btw writting : かえる and カエル ? Why is there two diff ways of writing it if its the same word ? Is there any difference ? In what case should i use one or other ??

Generally カエル is understood as "frog". We sometimes write the names of animals/ living things in katakana.

かえる is written with various kanji and each of then has the different meaning. We understand them by the context. Here are some of them.

帰る = be back, go back, come back, return...

返る = return...

変える = change, turn, shift...

買える = can buy

I hope this helps you.