The best way to understand how Crosslook works is to play with the Crosslook Generator and try creating embed code for your own web sites. But, in the meantime, here are a few examples:
This Definite Integral link will open a Crosslook viewer window that lists all the online assets that have been listed in the "Crosslinks" collection in MC3 as being related to the topic "Definite integral".
This other Learn about Definite Integral link launches the viewer but in this case it is only showing assets that have been identified as supporting "learning" about the topic "Definite integral", but is not showing assets that have been identified as application of the topic ("apply") or are simply un-categorized.
For an example of a Crosslook for another concept collection, here is one covering the topic Buffers from the Chemistry Bridge project. In this case the selection includes the combined assets from all the topics that are contained in the buffers topic ( Definitions of Buffers, pH of a Buffer, Henderson-Hasselbalch, and Buffer Titrations ).