I want to have a clear definition of journalizing. The importance of journalizing and how accounting entries are journalized

Journalizing is the original recording of a financial transaction, using debits & credits. It can be done in more than one manner, i.e. on a common two-column journal or using special journals where like entries are recorded together in one place. But it's still a way of recording the transactions. There is not much "definition" to it. It's more about knowing how to do it. And how to do it requires a lot of explanation of the rules of debits & credits, and knowing how to interpret transactions, and experience. And unless you ask a more specific question about that, I could write about two chapters in a book on the subject, which is a little infeasible. In other words, what you're asking is too vague.

The importance of it is that if they aren't recorded, none of the financial information of a company would be recorded. Not that "journalizing" is the only way to record anything, but it's certainly the common way, and it has to get recorded in some logical manner.