Interesting question! Well, inside most other fruits, like apples or pears, there are seeds. In fact, fruit is the plant’s way of spreading itself out, often by tempting other creatures to eating the fruit and… well, you can guess where the seeds end up!
The strawberry is a little different, though. Those ‘seeds’ on the outside aren’t actually seeds – they are the ‘true fruit’ of the plant. They are given the scientific name of ‘achenes’. And inside each achene is a seed! Hence, the strawberry isn’t actually generally considered a berry (nor, of course, is it made from straw!), but an ‘accessory fruit’ (http://en.wikipedia.org/wiki/Garden_strawberry).