こと is nominalization and so far to me (a student), the most important thing to learn in Japanese. It's how you take verbs or incomplete phrases and make them nouns. 食べること　は　よい　です。 Eating is good In the above example, 食べる was turned into the subject thanks to こと. With this you can make more complex thoughts. 映画を見ます- watch a movie 彼女　は　映画を見ること　を　ほしいです - She wants to watch a movie Here, こと made a "sentence" into an object. I hope this helps.

名詞として使いたいとき。 correct　 食べることは大切だ。 mistake 食べるは大切だ。