RNA splicing

RNA splicing is a stage in gene transcription. Messenger RNA (mRNA), which transfers the code from DNA to proteins, is built in two stages. 
In the first stage, each gene is translated into a pre-mRNA. Then the exons in pre-mRNAs are joined by splicing, which is done in the spliceosomes. 
This is needed because the gene is split into code sections called exons and non-coding sections called introns. The exons are brought together by splicing.
So, in molecular biology, splicing is a process where introns are removed and exons are joined. This makes the final mRNA. This messenger RNA is then used to produce a correct protein by translation. 
Alternative splicing.
In many cases, the splicing process creates a range of unique proteins by varying the exon composition of the same messenger RNA. This phenomenon is called alternative splicing. Alternative splicing can occur in many ways. Exons can be extended or skipped, or introns can be retained.
Eukaryotes vs prokaryotes.
Splicing occurs in all the kingdoms or domains of life, however, the extent and types of splicing can be very different between the major divisions. Eukaryotes splice many protein-coding messenger RNAs and some non-coding RNAs. Prokaryotes, on the other hand, splice rarely. Another important difference is that prokaryotes completely lack spliceosomes.
Discovery.
Phillip Sharp and Richard Roberts were awarded the 1993 Nobel Prize in Physiology or Medicine for their discovery of introns and the splicing process.
In 1977, work by the Sharp and Roberts labs showed that genes of higher organisms are "split" or present in several distinct segments along the DNA molecule. 
The coding regions of the gene are separated by non-coding DNA which is not involved in protein expression. The non-coding regions, the introns, are cut from the precursor mRNAs in a process Sharp called "splicing". The split gene structure was found to be common to most eukaryotic genes.