Micronutrients are trace elements, like copper, zinc, iron, boron, etc.... though used in much smaller quantities than N-P-K-, they are just as important. They ensure proper cell functions and the plants ability to make, store energy, utilize mobile nutes, etc.
PH balance refers to a mediums alkalinity or acidity. 7.0 is neutral. Anything higher is alkaline, and lower is acidic. Most nutrients beneficial for soil growers can be utilized in a PH of about 5.0 - 8.0, with 6.5 being the recommended.