Transcription is the process by which a cell transfers the information contained in the DNA to RNA molecules. This is regulated by many regulating proteins called transcription factors (both positive and negative) and executed by the RNA polyerase, an enzyme that has a few differences between prokaryotes and eukayotes, and the same thing happens with the type of regulators.
Eukaryotic transcription requires the formation of a initiation complex whichs is disaggregated once it starts.
Due to the abscense of nucleus in prokaryotes, transcription takes place in the cytoplasma, where the RNA molecule can be translated simultaneously. Moreover, eukaryotic RNAs suffer post-transcriptional modifications, while prokaryotic do not, but this last one can contain more than one gene in one RNA molecule (thats why they are called polycistronic).