The time of day is on the x-axis and the futures contract price is on the y-axis.
The prices go from 0 to 100.
The candidate with the highest futures contract price is the most likely to win the Iowa Caucus (according to the buyers and sellers of the futures contracts).
Unfortunately, these charts only indicate which candidate will probably win first place. It does not predict what place the non-first-place candidates will finish in.
Also, the charts are updated constantly (just refresh your browser), so there may be lead changes.
How did the charts predict the Iowa results?