I'm not sure how much explanation you want. The short answer is that TTL (transistor-transistor logic) is an older logic family, while CMOS (complementary metal

I'm not sure how much explanation you want. The short answer is that TTL (transistor-transistor logic) is an older logic family, while CMOS (complementary metal oxide semiconductor) is what's used nowadays, such as in microprocessors. In more detail, first there were bipolar transistors (NPN and PNP) and later MOS transistor (NMOS and PMOS). Bipolar transistors are your basic semiconductor transistors with three layers of semiconductor. MOS (metal oxide semiconductor) transistors have an insulating oxide layer between the silicon and the metal (or polysilicon) on top. MOS transistors were developed later than bipolar, and started to become popular in the 1970s. One type of logic that you can make from bipolar transistors is TTL (transistor-transistor logic). TTL is better than earlier logic families such as resistor-transistor logic (RTL) or diode-transistor logic (DTL). TTL was cheap, reliable, fast, easy to use, and popular with minicomputer manufacturers. TTL has two main problems, though. It uses a fair bit of power, and you can't make it very dense. I.e. you can't put a lot on a chip. MOS, on the other hand, has the advantage that you can make very dense circuits from it. (I.e. Moore's law applies.) NMOS was used for early microprocessors such as the Z-80 and 6502. The problem with NMOS is that it uses resistors (sort of) in the logic gates, and these waste power. The solution was CMOS, complementary MOS. You use both NMOS and PMOS transistors (the complementary part), and you can get rid of the resistors, and your chip uses very low power. The problem with CMOS is it's more complicated because you need two types of transistors, and twice as many (sort of). However, the need for low power won out in the mid-1980s and microprocessors such as the 80386 started using CMOS. Use of CMOS has continued to the present. I'm oversimplifying the history somewhat. The books "To the digital age" and "History of semiconductor engineering" go into much more detail.