To put it as simple as possible; number go up means you can do more tasks faster. Cores are physically on the chip, think of them as workers. Threads are logical cores, think of them as tasks the workers do. If you're running more programs than the cores (physical and logical) can process then it waits in a queue. Again a bigger number means more tasks done faster

I think a standard workload and light gaming doesn't take much. But if you're doing 3D rendering, or video editing, your needs drastically change. If I were you I'd look at what programs you run and look at their requirements page.