Answer 1

GET

http://localhost/index.php?KEY=VALUE

$_GET[KEY] // This return: VALUE

Exemple 1
http://localhost/index.php?id=10

echo $_GET['id']; // return 10

Exemple 2

http://localhost/index.php?name=Gabriel&age=18&country=Brazil

$_GET['name']; // return: Gabriel
$_GET['age']; // return: 18
$_GET['country']; // return: Brazil

POST

file: index.php

<form action="getPostData.php" method="post">
<input type="text" name="name" />
<input type="text" name="age" />
<input type="text" name="country" />
<input type="submit" value="send" />
</form>

file: getPostData.php

echo 'name: ' . $_POST['name'];
echo 'age: ' . $_POST['age'];
echo 'country: ' . $_POST['country'];