Copying part of DNA into RNA?

Transcription 'trancribes' DNA into RNA using RNA polymerase. DNA is made up of regions called introns and exons. Introns are regions that don't have any protein coding DNA, and so when the 1st copy of mRNA is transcribed, these intron regions need to be spliced out. Spliceosomes splice these intron regions out of the premRNA which is then turned into pure exon coding region mRNA. This mRNA then travels to RER to the ribosomes for translation into an amino acid chain, i.e. protein.