Gender in English: He, She or It?

English grammar states that people are referred to as 'he' or 'she' and that all other objects are referred to as 'it' in the singular or 'they' in the plural. In many languages, such as French, German, Spanish, etc. objects have gender. In other words, things are referred to as 'he' or 'she'. English students quickly learn that all objects are 'it', and are probably happy because they don't have to learn the gender of each object.

I live in a house. It's in the countryside.
Look at that window. It's broken.
I know that's my book because it has my name on it.

He, She or It With Animals

When referring to animals we run into a problem. Should we refer to them as 'he' or 'she'? When speaking about animals in English use 'it'. However, when speaking about our pets or domesticated animals, it's common to use 'he' or 'she'. Strictly speaking, animals should always take 'it', but native speakers generally forget this rule when speaking about their own cats, dogs, horses or other domestic animals.

My cat is so friendly. She'll say hi to anyone who comes to visit.
My dog loves running. When I take him to the beach, he runs for hours and hours.
Don't touch my lizard, he bites people he doesn't know!

Wild animals, on the other hand, usually take 'it' when spoken about in a general way.

Look at the hummingbird. It's so beautiful!
That bear looks like it's very strong.
The zebra in the zoo looks tired. It just stands there all day long.

The Use of Anthropomorphism

Anthropomorphism - Noun: The attribution of human characteristics or behavior to a god, animal, or object.

You often hear wild animals referred to as 'he' or 'she' in documentaries. Wildlife documentaries teach about the habits of wild animals and describe their lives in ways humans can understand. This type of language is referred to as an 'anthropomorphism'. Here are some examples:

The bull stands his ground challenging anyone to a fight. He surveys the herd looking for a new mate. (bull - male cow)
The mare protects her foal. She keeps a look out for any intruder. (mare - female horse / foal - baby horse)

Anthropomorphism is also used with some vehicles such as cars and boats. Some people refer to their car as 'she', while sailors commonly refer to ships as 'she'. This use of 'she' with some cars and boats is probably due to the intimate relationship people have with these objects. Many people spend hours with their cars, while sailors can spend most of their lives aboard ships. They develop a personal relationship with these objects and give them human traits: anthropomorphism.

I've had my car for ten years. She's part of the family.
The ship was launched twenty years ago. She's sailed around the world.
Tom's in love with his car. He says she's his soul mate!

Nations

In formal English, especially in older written publications nations are often referred to with the feminine 'she'. Most people use 'it' in modern times. However, it's still quite common to come across the use of 'she' in more formal, academic or sometimes patriotic settings. For example, some patriotic songs in the USA contain feminine references. The use of 'she', 'her' and 'hers' is common when speaking about a country someone loves.

Ah France! Her bountiful culture, welcoming people and amazing cuisine always call me back!
Old England. Her strength shines through any test of time.
(from Song) ... bless America, land that I love. Stand beside her, and guide her ...