In parashat Tetzave the Zohar talks about the different Holy Names. This names have different purposes such as meditations. Two of the most famous set of names are the 72 Names of God and the 42 letter name of Hashem. In  the Torah, the Zohar explains, there are times that one letter is written bigger than the rest of the others. This can be seen in the verse of the Shema Israel where the Ayin is bigger so does the final Dalet. The Zohar is comparing this phenomenon with the different types and purposes of the Names of Hashem. 

There are three levels of the Holy Names. The highest level of Names are so strong that just by meditating on them, they get activated and fulfill their purpose. The middle level is composed by the names that in order to be activated, the person needs to say the name out loud. To use the power of speech. The lower set of names are also related to the negative side. These names can be activated through an act. This is what is called Kabbalah Ma’asit...