The factors affecting the performance of the CPU: clock speed, number of cores, cache.
A higher clock speed generally means more performance, as the computer can do more operations per second due to this. However, a higher clock speed also means the CPU will run at a higher temperature, so will require better cooling in order to dissipate this. If the CPU runs too hot for any period of time, it can cause damage to the CPU, reducing its lifetime.
Multi-Core Processing allows the CPU to perform more than one action at once, by doing each on a separate core. This means that the CPU will run faster on multi-threaded workloads, where the program has been written to take advantage of multiple CPU cores, or when multitasking.
There are three levels of cache, L1, which is the smallest and fastest, L2, which is the medium, and L3, which is the largest, but slowest.