Answer: Gematria is a specific inner state of a person or of his soul, comprised of desire (a vessel, Kli) and Light, fulfillment. The sum of all sensations, impressions, states, memories, and intentions, the general state of the soul expressed in the form of letters or a sequence of letters, is called Gematria. It is a way of writing down a specific state of the soul.
Suppose I could play a melody or sing a song that expresses my state. This is Gematria. I can draw a letter or symbol; this will also be Gematria. I can convey my sensation or my state by recording it. It is similar to Reshimo, a record of information about a state.
In spirituality there is nothing besides the state of the Light and desire (Kli), that state of equivalence between the Light and desire with the help of a screen or intention. Everything else are means or ways to express this state.
From the 2nd part of the Daily Kabbalah Lesson 8/15/10, The Zohar