Itanium is a type of computer processor, kind of like the brain of a computer. It was invented a long time ago by two companies, Intel and HP. They made it so that it could do lots of different things all at once, like helping you do your homework, play games, or watch videos.
Imagine the Itanium like a really big puzzle that has lots of pieces that can work together very quickly. Each piece is called a "core," and the more cores your Itanium has, the faster it can work. It's kind of like having lots of helpers when you're doing something really complicated, like building a big Lego castle. If you have more helpers, you can build the castle faster.
Itanium is used in things like big servers, which are like really powerful computers that are used by businesses or governments. These servers need to be able to do things very quickly and handle lots of different tasks all at the same time. Itanium is good at this because it has lots of cores, so it can handle lots of different things at once.
But not many people use Itanium anymore because other types of processors, like the ones made by Intel and AMD, can do the same things but are cheaper and easier to use. So, Itanium is kind of like an old puzzle that people used to play with a lot, but now they have new puzzles that are more popular.