gene expression

GE is the process of a specific gene producing a specific information to synthesize a functional gene product. During  gene expression process may be modulated by the transcription, RNA splicing, translation, and post-translational modification of a protein.  

Gene Product: protein and RNA
https://en.wikipedia.org/wiki/Gene_product

Regulation of GE:  
The basis of cellular differentiation and morphogenesis is the gene regulation that gives the cell control over structure and function.
Mechanisms that are used by cells to increase or decrease the production of specific gene products, and is informally termed gene regulation. It is very critical for an organism for normal development to regulate gene expression levels.

phenotype vs genotype:
The genotype gives rise to the phenotype, i.e. observable or physical trait at the level of gene regulation level.