mRNA stands for messenger Ribonucleic acid. The role of mRNA is to carry genetic information for the synthesis of protein from the nucleus after transcription.
After the transcription process is over, the mRNA leaves the nucleus and heads to the ribosomes in the cytoplasm where translation of this information takes place.
The ribosomes are the work bench of the cell. They receive the mRNA with its coded information, read it and translate it and with the help of tRNA (transfer RNA), amino acids are fetched from the cytoplasm and linked together to form the exact protein that was coded for on the mRNA.