At the beginning, you can distinguish one from another because:
Dot product: your result is a number
Cross product: your result is a vector.
They have several applications, especially in vector functions and applied mathematics, and in electromagnetic theory too. So for now I am only referring to Analytical geometry here.
Dot product: it's related to the angle between two vectors, so the sign of your result can help you to identify if your vectors are perpendicular, or if they have an obtuse angle between them (if your result is negative).
Cross product: mostly used to calculate vectors perpendicular to the plane, or also to describe the particular condition of parallelism. You can calculate this other thing to find a parallelogram area:
|C| = |A*B| then
|C|=|A||B| sin alpha ==> it makes the area for a parallelogram generated by the vectors A and B, so |C|=area
I would advice you to check this topic in any Analytical Geometry book first, though.