Here is a link to the previous post.
Count Nouns
We use countable nouns when a word has singular and plural forms (word - words); (sentence - sentences); (book - books).
Mass Nouns
We use these when something is abstract or innumerable (bravery); (advice); (knowledge). Another use would be when we refer to a group of people or things that are in a group without any determination (the party); (the class).
Gender
When it comes to English language, nouns are a bit different as they don't have a true gender, something that you encounter in other languages. Feminine and masculine play a big role in Spanish or French, yet it doesn't determine the article we use in English. Though there are words that are masculine (dad); (wizard); (nephew) or feminine (mom); (witch); (niece), most still are common gender (baby); (child); (student).
Some words were once considered to be strictly masculine, especially when talking about working. Over time, though, they were accepted as common gender words (writer); (police officer); (judge).