OHC in general means OverHead Cam while SOHC means Single OverHead Cam.
In the SOHC engine the camshaft is installed in the cylinder head and valves
are operated either by the rocker arms or directly through the lifters (as
in the picture).
The advantage is that valves are operated almost directly by the camshaft -
easy to achieve the perfect timing at high rpm. Also it's possible to
install three or four valves per cylinder
The disadvantage - an OHC engine requires a timing belt or chain with