When do I use Masculine or Feminine words?!
How do I know when to use petit or petite? When do I use grande or grand? Arghh... confusion :[ If anyone could help I would be truly grateful x
The adjective (i.e. petit / petite) that you use depends on what you are describing.
le canard = is masculine, so use "petit" to describe it; la vache = is feminine, so use "petite"
un garcon = use "grand"; une fille = use "grande"
Matt is 100% right. Unfortunately, nominal gender (masculine and feminine nouns) is not an aspect of language that is learned, but rather acquired. In short, this means that it is truly something that will happen as you practice French naturally , and there is little value in trying to memorize gender as you learn nouns. It will happen anyway.
For the purposes of alleviating your confusion, simply know that ALL nouns fall into one of two groups. It is not necessary that you know them as masculine versus feminine.
I think Bidwell's answer is a little too vague. I think it's fine to understand that nouns have genders, and there are feminine nouns and masculine nouns. Here's the Wikipedia article on it: https://en.wikipedia.org/wiki/Grammatical_gender. Here's an article specifically on French genders: http://www.cliffsnotes.com/study_guide/The-Gender-of-Nouns.topicArticleId-25559,articleId-25484.html
Now, Bidwell's correct in saying for the most part you will just learn which nouns are which, but you will also quickly learn to predict them. Generally, things that are specifically about men or women have obvious genders -- un garçon (a boy, masc.), une fille (a girl, fem.), le père (the father, masc.), la mère (the mother, fem.). Other things won't be nearly as obvious (and sometimes seem backwards), but you'll get a feel for the common masculine and feminine endings of nouns (many of them are given at that second link -- don't try to memorize them!).
The point of all this is that the adjectives (big, small, etc.) all have to agree with the gender of the noun. So "grand" is the masculine version of big, and so you'd say "un grand garçon," while "grande" is the feminine version, so "une grande fille."
Sam, absolument vous avez raison ! Mais....
"Things that are specifically about men or women" might be more clearly stated this way:
The gender of nouns is self evident only when the subject is a person. All male persons are in fact masculine nouns. However, my 2 female dogs are grammatically masculine in gender. I know that we can say "une chienne," and that this is a valid lexical item. The context for my above example would certainly matter - if we are discussing dogs within the subculture of dog breeders, for example, "❤❤❤❤❤" implies no vulgarity. However, other contexts of the word "❤❤❤❤❤" are most certainly offensive, and perhaps purposefully so.
Additionally, Sam is 100% correct about the agreement of gender between adjectives and nouns. However, we should be careful to also note that gender agreement is insufficient; adjectives agree with the nouns that they describe in gender and in number. We mustn't forget to consider both gender and number when we describe.
My point is simply this - understanding nominal gender is largely inconsequential in the elementary stages of language learning (acquisition). Its inspection has value, but it is unfortunate (in my opinion) that so many language learning materials attempt to have learners consciously notice this language feature so early in the process.
Duolingo deals with this topic the right way (again, that is my opinion.) Gender is present in Duolingo instruction, but it is always contextualized and a component of meaning, rather than "teaching" the concept of gender and then asking learners to apply the rule. The former works, the latter creates grief and confusion.