DOHC is dual overhead camshaft
SOHC is single overhead camshaft, basically the DOHC version
produce more power.
V-TEC is Honda's version of variable valve timing and lift
electronic control, which is essentially the same as Toyota's
VVT-i, Mitsubishi's MIVEC(now known as MR which stands for
Mitsubishi Racing)etc.. btw, if u read the history, it was Honda
who came up with the idea first. V-TEC changes the valve timing
according to the rpm of the engine to produce optimum power, and
all this is controlled by the ecu. so if u want more power, go
change its settings 
as for TOHC, i'm not too sure(triple overhead camshaft? 
)
for cylinders, the more the merrier
. 4 cylinders equals 4 pistons(the blocks of metal that moves up
and down the engine when running), 6 cylinders equals 6 pistons and
so on. there r also different arrangements of the pistons. most
common for 4 cylinder is inline 4 or straight 4, where all 4
pistons r facing in the same direction. there is also horizontally
opposed arrangement, which is used by Subaru(Boxer engine) and
Porsche, and this provides better comfort due to lesser vibrations
being transmitted into the cabin. performance-wise, the boxer
engine gives better control due to better CG, however, it usually
produces a little less power than the inline ones when capacity is
low. there is also the V arrangement, which can be commonly found
in high-end sport cars like Ferrari, Lamborghini etc. however,
there is no engine with 4 pistons arranged in a V shape(harder to
maintain i guess). the more common ones are V-6, V-8, V-10(used in
F1) and V-12.
[email protected], i would appreciate if u could clarify if there is any TOHC
engines around
