To study and perform Naive-Bayes Classifier for Document Classification

What is the key assumption made by Naive Bayes in text classification?
In text classification using Naive Bayes, what does the term 'prior probability' refer to?
How are likelihood probabilities calculated in Naive Bayes for text classification?
What type of text data preprocessing is commonly performed before applying Naive Bayes for text classification?
Naive Bayes is commonly used in which type of machine learning tasks?