1 -> Bob
2 -> Joe
3 -> Sunny
4 -> Hannah
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If you follow that, then hashes aren't too difficult. The only effective difference is that they're not accessed by number. There's no particular order. Instead, it's like a dictionary, where you look up a definition by the word. You might create a hash called %race_results like this:

my %race_results = (
    first  => 'Bob'
    second => 'Joe',
    third  => 'Sunny',
    fourth => 'Hannah',
);
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Think of it like an array, where you use strings instead of numbers, and you'll have it. (It's not completely accurate under the hood, but that's how I first approached it, and it's a decent mental model.)

Use them whenever you have one string to associate with another, and you want to be able to look something up as you would in an encyclopedia or a dictionary. If you can look at the world in terms of indexes, you'll have your keys.

A hash lookup is the word "of".

So, for instance, if you want to be able to find the address of a person, you would name the hash %address, make the keys be the $name of the person, and addess the address with:

print "$name has an address of $address{$name}\n";
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I find this little tip to be very useful in figuring out where you can use hashes, what to call them, and how to read code written with them. After that take a look in the Cookbook for some of the hash tricks, and as you read them see how they fit in this mental model. The answer generally is, "Pretty well."