Okay, I'll try...
I only have one oracle deck, so I can only describe that. But from what I know about others, it basically has less cards than tarot (usually). The cards are also different, and can have other meanings. Like the one I have, Madame Endora's Fortune Cards, there are cards called 'The Key', 'The Dragon', 'The Raven', and so forth. But there is also 'Love', 'The Chalice', and 'The Knight', so some of the images are similar to tarot. The best thing about oracle cards, is that most of them dont have titles or captions, so you can basically make up your own meaning.
Its all about what the card pictures, and what it means to you. But all in all they're not that different from tarot. Hope this helped.