The first is a change to Chakra's JIT compiler that adds support for x64 and ARM architectures. This allows it to execute directly on the CPU granting it more flexibility and speed. This is used to reduce the amount of machine instructions for code thus reducing memory footprint.
The third has Microsoft improved property access. In IE9, Microsoft utilized inline caches that could remember shapes of objects and the corresponding location in the object's memory where a property can be found. The only problem was that it could only remember one object shape at at time. With IE10, Microsoft has introduced a secondary caching mechanism that will allow the operation of code on objects of different shapes.
If you're confused after all of that, just know that Internet Explorer 10 is a beast. Microsoft is being really aggressive about making their latest browser one of the best on the market. If you use Windows 8, IE10 isn't a bad choice at all. If you still don't trust IE after all the years of betrayal, you can now download Chrome for Windows 8.