Tarot is a certain type of set up. It always has 78 cards with the two arcana sets. The minor arcana is made up of four suits wands/rods, pentacles/coins, cups/chalices and swords. These suits all relate to one of the four elements of earth, air, fire and water. All the cards have two meanings depending on if it comes up in a reading as upside down (reversed) or right side up. If you learn the basic tarot card meanings, you can read any tarot deck even if it goes to a theme where they change up the suits. For example I have a witchy tarot that uses boulders for coins/pentacles but since I know this I can read it the same way I would a standard tarot deck.
However, oracle decks are all different. Its just a set of cards based on anything. You can find them over topics like runes, ogham, mermaids, fairies, plants, medicine wheel, and etc. These can have any number of cards in the deck too. People who do not connect well to tarot cards generally go to oracle cards by finding a deck they like. For example, if you like herbalism you can find an oracle deck based on trees, ogham or herbs to use. Most people like that you can find decks over a topic like this that you love. Also when reading the cards, each deck is different. Some use reversed cards while others don't do that...some also come with suggested spreads that are unlike what you would use in tarot decks.
That's the basics of it. If you have any question about this that I didn't answer, just let me know.