여행 is a noun, by itself, but you need 하는거 for words that are inherently verbs, to make it into a noun.

Example: 행복 = Happiness 행복해 = to be happy 행복하는거 = (the action of) being happy (followed by a description)

걷다 = to walk 걷는거 = (the action of) walking (noun of verb)

저는 행복해 I am happy

행복하는것은 좋아요 Being happy is good

저는 집에 걸어요 I walk home

집에 걷는것을 힘들어요 Walking home is tiring

Those are the same haha

Open on web and read tips and notes of gerund, it's all there.

Actually the meaning is the same, just 중요합니다 more formal than 중요해요

The first is polite form, the latter is formal form. Essentially they are/ mean exactly the same thing.

The conjugations (way the verb ends) are different depending on to whom you are speaking. One has more formality than the other. Do you want to guess which one?

중요합니다 is more polite

The meaning is the same. They're used depending on who you're talking to. 중요해요 is Polite (strangers and people older than you) and 중합니다 is Formal (your boss/teacher)

It's just a polite matter

It is the same. 중요합니다 is the most polite form between two of them