The varieties of orthographies in the world amaze me and aesthetically Tibetan is one of my favorite. Below I made a diagram which captures all the key basic points needed to understand basic Tibetan orthography.
The top half of the diagram shows the basic syllable structure of stacked letters. Note that though prefixed letters are silent, the exceptions are listed below. The bottom half of the diagram illustrates sub and superfixed letters and how subfixed letters change the pronunciation of the root letter. Superfixed letters are silent.
While the Tibetan language evolved, old spellings persisted making the rules of pronouncing Tibetan extremely complex — much more complex than English’s orthography.