There have been two variations of Blast/Explosion release shown throughout "Naruto"'s history. However, Deidara's clay variation is of little concern during this training. The variation i'll be learning was used by Gari and thought to be the collaboration of earth and lightning style chakras. The result, being the blast kekkei genkai, allows the user to manipulate their chakra to give it explosive properties which can be devastating in battle.
The techniques work upon contact with objects. So taijutsu is often, the basis for which blast techniques can be executed. Requiring contact can be dangerous for the user, because it opens up a variety of situations an opponent could take advantage of it the Blast user cannot make contact with the target.
The element is weak to lightning and water, although effective against wind and earth.