Often when shopping for a processor, you come across numbers called lithography figures, or manufacturing process indices, like 28nm, 14nm or so.
The lithography figures tell you how tightly packed transistors are inside your processor, i.e how close they are. The lower the distance between two individual transistors, the faster electrons can travel between them, and the lesser energy that’s wasted in transit. This means a lower thermal output across the board and more efficiency which translates to more speed with lesser power consumption.
An AMD Athlon 64 from 2005 has a 90nm manufacturing process.
A typical Core 2 Duo from 2007 has a 65nm manufacturing process.
Haswell/Broadwell processors use 22nm.
The latest Kaby Lake processors use 14nm processes.
Meanwhile on the ARM side of things, things have progressed as far as 10nm on the Snapdragon 845, enabling higher efficiency and longer battery life.
