Hyper threading as it relates to CPU.
Hyper threading enables a CPU to handle tasks more efficiently and resourcefully. It means the CPU can multitask without degrading system performance. Hyper threading was first made to work with x86 based CPUs such as Pentium 4. Now even Intel atom uses the hyperthreading technology. Hyperthreading makes a CPU like Pentium 4 behave as a dual core, but these cores are virtual, and they share the same computing resources but are efficiently managed.
Multicore as it relates to CPU
A Multicore CPU is a CPU capable of advanced multitasking using physical cores that have their own separate computing resources,( not shared). It is like plugging two or more individual processors into one integrated circuit. A CPU with multiple cores means that each core can be assigned to different tasks. However, if a core cannot adequately handle the task assigned to it, other cores can jointly assist to finish the task.
Most CPUs have their speeds clocked. However, some specially designed CPUs have adjustable clock speeds. The reason why most CPU speeds are clocked is to prevent them from burning out. Interl CPUs that can be overclocking capabilities have the letter K in their name while that of AMD is called black edition.