Use the prefix mono (one) and di (two) to help you remember the differences between these two flowering plant types.

Flowering Plants are separated into two distinct groups, although there is some gray areas with certain plants.

Monocots produce one leaf from the seed after germinating; dicots produce 2

Monocots produce parallel leaf veins; dicots produce a net-like display of veins.

The differences continue and become more scientific.  Try the link below from Wikipedia to begin with if you need more information.

There are several differences between monocots and dicots, here are three big ones.  The main one (that gave rise to the names) is that monocots have seeds that are one piece (like corn), while dicot seeds can be easily split in half (like peas). Other differences include that monocots have flower parts (like petals) in multiple of threes while dicots usually have them in multiples of 4 or 5.  In terms of the leaves, monocots exhibit parallel veins while dicots have reticulated (net-like) veins.