What is a "M cache" in a CPU's specs and why is a multi-core CPU better than a single CPU ?

[JADOLLA]

What is the role of a "M cache" (what does the "M" mean) and is the CPU MUCH MORE expensive when it has more "M cache"
And why is a multi-core CPU better than a single-core CPU and what is the best multi-core CPU to buy (mean if its a Dual-core, Quad-core…) it doesn't include the company nor the frequencies.

 

[turkey3_scratch]

The cache stores temporary data that the CPU can use to remember for repetitive tasks, making stuff more efficient. For example, if there is a equation which must be repeated multiple times, instead of doing it all over it might remember or put some part of it in the cache to do the rest quicker.

Multiple cores is like many CPUs in one. Not all cores are always used, but each core can be calculating its own thread of data rather than relying on one central unit. For example, one program's data can be calculated on one core, such as a game, and the OS on another, which brings efficiency.