Genetic engineering is a broad term that describes any artifical process where DNA is manipulated to contain new or novel combinations of genes.
Basically this includes:
The joining together of DNA from two or more different organisms (recombinant DNA) which are then inserted into a host cell
Isolating a strand of DNA that contains a particular gene, removing the gene and re-introducing the modified DNA (splicing)
Creating artificial strands of DNA for insertion into a host