about cheers


i am asking about cheers , is a kind of greeting word?
is it correct to use it as Hi ?,
the last question is is it formal or informal?

thank you so much

‘Cheers’ as in emails is an informal complimentary closing. It is a way of saying ‘good-bye’.

What’s the meaning when use ‘cheers’ in a party (e.g. before start taking a drink)?

There’s no meaning. It 's just a word people use as a ‘toast’ to each other.