Answer: mRNA (messenger RNA) is formed from a template of DNA ( deoxyribonucleic acid) with the help of enzyme RNA polymerase. This process is called transcription.
pre mRNA needs to undergo processing before it can be translated to form protein (in the cytoplasm). It involves splicing ( where introns that is non coding sequences, are removed and exons are joined).
Apart from this, it includes capping at 5' end ( so that it is recognized by ribosome for translation) of mRNA and addition of poly A tail at 3' end.
The sequence for editing is depicted in the attached flow chart.