Pictographs resemble what they mean. For example, a pictograph
of "Tiger" would be more or less recognizable as the image of a
tiger crudely drawn.
Ideographs do not resemble what they mean. However, Ideographs
can resemble one another (i.e. the ideograph of "Tiger" may
resemble the ideograph of "Lion", but neither would resemble a
Tiger or Lion crudely drawn). Ideographs can also steal phonetic
pieces (i.e. The ideograph for "Shipping" may have the ideograph
for "ping" in it since "ping" is phonetically part of "Shipping").
Finally Ideographs can be composed of multiple minor ideographs
working in concert (i.e. "Archer" may be written as combination of
"bow" and "man" since the Archer is man who uses a bow). None of
the combination-elements are present in pictographs.