What's the difference: pentium 4-M, pentium M, celeron M, atom, Amd, core duo, core 2 duo; all 1.8 Ghz. Do they all imply the same speed, or are they different though having the same 1.8ghz? Pls guys help. I need to know the relationship.

All the processors mentioned above are all Intel processors except the AMD (Advanced Micro Devices). I'll try not too go too far by trying to make a distinction between the Intel processors listed above. The pentium 4-M, pentium M, celeron M, atom, core duo, core 2 duo are all Intel processors like I said earlier.

Breaking all these processors down into their various families, the pentium 4-M (laptop version of pentium 4)  and pentium M (the "M" stands for "mobile"  fall into pentium family. The pentium M should not be confused with pentium 4-M (the laptop version of the Pentium 4). Pentium M is designed specifically for laptops. Since each clock cycle uses battery life, the Pentium M was designed to "do more" with each clock cycle, so that its overall performance would still be on par with the higher clock Pentium 4-M's, while providing longer battery life. A 1.6 GHz Pentium M can typically attain or even surpass the performance of a 2.4 GHz Pentium 4-M.

Celeron M: Intel Celeron family is a line of "budget" x86 processors based on Pentium designs. Priced lower than their Pentium counterparts, the Celeron processors have certain high-end processor features disabled (like dual processing or multiprocessing). This is why you find laptops or desktops with celeron processors to be cheaper. The Celerons are also slower than similar-clocked Pentiums due to smaller L2 cache size and sometimes slower bus speed.

Atom Processors: A family of small, low-power CPU chips from Intel. Atom provides x86-based computing in low-cost, handheld devices and ultra-compact computers. The Intel atom processor is designed specifically for "Net Books". Net books are the little brothers (or sisters) of notebooks but above the average PDA. So they're like a littler notebook. The performance of a single core Atom is about half that of a Celeron of the same clock rate. I guess the Intel Atom was designed for low power consumption. My conclusion ? Atom has low energy consumption but slow, celeron is faster than Atom but bigger power consumption.

Dual core family: Dual core is simply a generic term referring to any processor package with two physical CPUs in one. The Core Duo is Intel's first generation dual core processor based upon the Pentium M (a Pentium III-4 hybrid) made mostly for laptops (though a few motherboard manufacturers have released desktop boards supporting the Core Duo CPU), and is much more efficiently than Pentium D (The Pentium D is simply two Pentium 4 Prescott cpus inefficiently paired together and ran as dual core).
The Core 2 Duo is Intel's second generation (hence, Core 2) processor made for desktops and laptops designed from the ground up to be fast while not consuming nearly as much power as previous CPUs.
The difference between Core Duo and Core 2 Duo?: These are micro-architectures for how the CPU operates. Core Duo was Intel's first dual core architecture, and Core 2 Duo is the "sequel" to Core Duo.  So you see, a CPU can be a Core Duo with 2 cores, or it can be a Core 2 Duo with 2 cores. They are both dual core -- the difference is the micro-architecture. Simply put, Core 2 is a faster, more powerful micro-architecture.