Translation:The cat is fat.
Hi. I'm korean. This is focus. 뚱뚱 is fat. but if you use this word. You can't use for adult. it's not comeon. Good luck
Do you mean etymology? Korean has a lot of these repeating verbs. I don't know the true etymology, but it's a good mnemonic for me to think of them as onomatopoeia
Ya. 합니다 is to be/am/are. 이에요 and 예요 are the same but less formal. You'll learn that later.
Why is this 합니다 rather than 습니다? I am struggling to find the rule for this
When the verb stem ends with vowel, it connects with ㅂ니다, while for consonant, it will be 습니다
Examples of vowel end 마시다 > 마십니다 (drink) 좋아하다 > 좋아합니다 (like)
Examples of consonant end 먹다 > 먹습니다 (eat) 좋다 > 좋습니다 (good)
It depends if the verb stem has 하다 (kind of a multipurpose be/have verb - reminds me of faire in French)