Okaki (おかき) and arare (あられ) are rice crackers made of glutinous rice (mochi rice).
Nowadays, the only difference between them is their size. Okaki is bigger than arare.
But it used to be that okaki were broken into pieces with a hammer while arare were cut into small pieces with a blade.
These wagashi (traditional Japanese snacks) should not be confused with senbei, which is made from a different type of rice.
They can be baked, roasted or fried.
By adding different ingredients to the exterior or the dough itself, many variations of okaki and arare can be made.
I believe that there are easily over 40 types of these rice crackers in Japan.
The most famous is probably hina arare (雛あられ), which is traditionally eaten during the hinamatsuri, a religious holiday in Japan.
Here’s an Amazon link for you to try a norimaki arare.