When you have two unique consonants that together have a single sound that chunk of consonants is referred to as a "consonant diagraph". The most common starting diagraphs are sh, ch, wh, and th. These diagraphs are often referred to as the “h brothers”. You will find these to be the most common jump off points for students in preschool or kindergarten. I always like to start with "sh" by shutting out the lights and saying, well you can guess where I am going with this.
The most common words formed by this diagraph are- suffixes: each, pitch, rich, lunch, and such. prefixes: chair, chin, chip, child, and cheek