Genomics and Transcriptomics are important parts of Bioinformatics. In general, Bioinformatics is known as part of science that collects and analyze biological data. It's often about big amounts of data obtained from next-generation sequencing. I don't know exact definition, but genomics can be understood as DNA analysis and Transcriptomics as RNA research.

Genomics and Transcriptomics are both comprised of

planning,

wet lab,

data analysis.

Bioinformatics should be part of planning, certainly is a major component of data analysis.

Bioinformatics can be about other biological data, too.

Bioinformatics skills are the skills to develop methods for computationally analyzing biological data, and the skills to apply such method.

Genomics is a component of Bioinformatics that used tools and techniques to analyse huge data to reveal scientific discovery.