Looking at the poorly translated link you provided from Wikipedia shows where your confusion is coming from.
In the opening chapter of Sefer Yetzirah, the Hebrew alphabet is conceptualized as falling into three general categories of meaning. They are referred to as Counting, Writing and Speaking.
What this means is that proper and complete comprehension of Hebrew as found in the Holy writings encompasses the numerical meaning of the letters (The Hebrew letters have numerical meaning. Numerical and mathematical transformations of all types give additional meaning and understanding to any text.).
Additionally, the form of the letters themselves, meaning how they are formed both when they are engraved like in the Tablets of the 10 Commandments and when they are written with ink and pen convey additional levels of understanding in terms of any text. This also relates to the traditions of large and small letters, reversed letters and other types of transformations pertaining to the form and shape of the letters and also the number and types of crowns found on different letters.
And the third category is how the letters are pronounced and spoken. This encompasses both variations where the letters are written one way and the reading or pronunciation of the text is different and also in regard to what part of the mouth and throat the pronunciation of those letters originates from. Those which originate from the same part of the mouth are interchangeable. It also relates to the whole subject of Nekudot, which can be thought of as the vowels in Hebrew and Ta'amim, also known as Trope, which can be conceived of as a type of punctuation marks. But they also have a much deeper meaning relating to the flow of a given text. This too is a very large field of study unto itself. Also included in this division is the general subject of grammar, verbs and nouns as it relates to Hebrew.
What follows in the translation of the Wikipedia link explains how these three categories of Counting, Writing and Speaking also correspond to the three divisions of the letters themselves, the 3 Imahot, the 7 Doubling Letters and the 12 Plain letters. And the rest of Sefer Yetzirah goes into further explanation of all these arrangements and how they are the basis and model for the existence and structure of all of Creation.