The aliases feature in Prestashop is a excellent feature that allows you to anticipate users search behaviour when they enter incorrect or similar words. Most php carts do not cater for this, but Prestshop does.
Within Prestashop you can therefore create aliases to help your shoppers find what they are looking for when they may mis-type a word. For example, instead of typing ipod, they could mis-type and search on piod or ipdo. Or color is USA is spelt colour in the UK.
Go to BackOffice>>Tools>>Aliases

You now have a list of any alises that already exist, you can change the status of each alias in the list, edit or delete it using the icons.
click "Add New"

You now enter the aliases words, each seperated by a ",".
In the result field, enter the product this alias should take the visitor in the search results. (Basically add all the aliases for a single product (the result) as a comma seperated list), save and then add new for the aliases you wnat to input for another produuct result
When you save each alias will be listed seperatly in your main list (Fig 1)
Now when your web user enters piod into the seach option, they will see all products that they would have seen had they enetered ipod.