I don't have a biological question therefore, this might be be quite basic. But I want to know does genomics entail population genetics or these are completely different fields?
They are different. Genomics is the general science of sequencing whole genomes (or sometimes, the majority of the genome, or all the protein-coding genes, as in transcriptomes). Population genetics uses molecular data (usually DNA sequences, but not always) to make deductions about the characteristics of a population, or the relationships among biological populations. Genomic data could be used to draw conclusions about population genetics, but genomics can be used in many other sciences, and population genetics can be performed with other kinds of data besides genomes.