Okonomiyaki is definitely a soul food people in Osaka region. The people of Osaka loves KONAMONO(flour stuffs) as like okonomiyaki, takoyaki(octopus balls) and udon noodles.
Okonomiyaki is a savory pancake with pork of seafood(prawn, shrimp, cuttlefish, squid, clams and etc), covered with okonomiyaki sauce(sweet & salty), mayonnaise, seaweed powder and bonito flakes. Then, there are several flavors. Butatama means pork and egg. Ikatama means cuttlefish and egg. Modanyaki comes with yakisoba noodles.
Mostly you have to go to okonomiyaki restaurant to order okonomiyaki(although many izakaya-Japanese tavern offer okonomiyaki but it is not the REAL one), and the staff will prepare it in front of you on the large iron plate which is mounted into the table.
By the way, there is also Hiroshima style okonomiyaki which is also popular not only in Hiroshima region but also in other regions but Hiroshima style must be with yakisoba noodles or undon noodles and mostly not prepared at each table.
Then, almost no okonomiyaki restaurant offers both styles. Therefore if you want to eat Hiroshima style okonomiyaki outside of Hiroshima, please read carefully the signboard. If you just say I want to eat okonomiyaki, 99.9% of Japanese will lead you to non-Hiroshima style in Osaka. May be 80% of people in Tokyo too.