Gene annotations refer to the comprehensive information that describes the functional elements and attributes of a gene within a given genome.
These annotations include details such as gene names, locations, coding sequences, exons, introns, transcription start and stop sites, and regulatory elements.
The point is the NGS sequencing machine output just provides a sequence of base pairs and does not mark the start and end of genes, exons etc, that has to be done separatelly.
Gene Annotations is done using computational tools, experimental data, and biological literature, and serve as a key resource for understanding gene function and structure. Annotations can also specify alternative splicing events and different isoforms produced by a single gene. Gene annotations are crucial for interpreting genomic data, guiding variant analysis, and enabling researchers to link genetic variants to potential phenotypic effects.