They all can used to imply that something is necessary. Vital also has a dual meaning (like most English words) of, full of life or lively. Crucial is used for something that is necessary in the success of failure of something.

Hello, Katerina. Nice to meet you. These words basically mean the same thing. The word "vital" could me more appropriate when talking about health-issues (vital signs) and "crucial" can be used when making decisions etc. I hope this helps.

They are synonyms. Meaning, they mean almost the same thing. In this case, they mean the same thing. Crucial: whatever the subject is, it’s needed  Vital: it’s a very important part of the subject Essential: it is needed, and it can not go without it. 

Hey Katerina how's it going? My name is Alberto and I am a native Spanish speaker from Mexico city. I am an avid reader and language learner. in my free time I enjoy running, meditating and playing chess. I am sure that we could make a good team to practice languages. I will be more than happy to help you out to boost your English Please let me know if you are interested We may to talk about those words that you put above