When it comes to CPUs, the performance specification of 2 GHz means different things depending on the particular model of processor. In general, though, a 2 GHz CPU is going to be a pretty powerful one.
For example, Intel's Core i7-8700K processor has a base clock speed of 3.7 GHz. But, with Intel's Turbo Boost technology, it can automatically boost its clock speed up to 4.7 GHz when needed. So, in terms of raw speed, a 2 GHz CPU is going to be considerably slower than something like the Core i7-8700K.
However, clock speed isn't the only thing that determines a CPU's performance. There are also things like the number of cores, the cache size, and the instructions per clock (IPC) rate. A CPU with a higher clock speed but fewer cores, for example, isn't going to be as powerful as one with a lower clock speed but more cores.
So, when it comes to the performance specification of 2 GHz, it's important to look at the whole picture and not just the clock speed. But, in general, a 2 GHz CPU is going to be a pretty powerful one.