Ok, let me try,

insert effect is the when you send the whole signal to the effect processor and apply the whole effect on the signal (of course, some some effects processors allow you to apply the effect on part of the original signal, if this is the case, they will have dry/mix percentage) and then when they return, they actually return to same point of insertion for that individual track/channel.

send effects is when you send part of the signal and apply the effect processing on that particular part but the signal is not returned at the point of send but to the stereo master bus that is shared with all other channels or tracks. So the "unsent" part of the signal will go through the pan and eventually be mixed with the "sent" portion of the signal.

I wonder if I got it right.