gDNA is genomic DNA present in every cell. This is in contrast to cDNA which is complementary DNA synthesized by inverse transcriptase on an RNA template.
gRNA is guide RNA that brings Cas enzyme to the exact DNA or RNA sequence to cut. See this What is CRISPR?
Note that cDNA represents the expressed genes only, not the whole genome. It is complementary to the mature mRNA, so it lacks the intron sequences. It is suitable for recombinant DNA intended for protein production.