what is mRNA ?

waht is mRNA in a virus? It is genetic material that could specify the virus as its own but not others.
and does mRNA related to RNA? mRNA is one type of RNA, there are some other types of RNA, such as tRNA.
The function of all RNAs are related with the synthesis of proteins, but each takes the different role. mRNA is provide message of protein structure, a group of tRNAs are carriers of specific amino acids, and ribosomal RNAs provide a platform for installation of amino acids into proteins.

Generally, there are three types of RNA:
messenger RNA(mRNA), transfer RNA (tRNA) and ribosomal RNA (rRNA).Messenger RNA (mRNA) carries information about a protein sequence to the ribosomes.

mRNA is just a subset of RNA.

Messenger RNA (mRNA)
（信使核糖核酸）

携带遗传信息，在蛋白质合成时充当模板的RNA。

从脱氧核糖核酸（DNA）转录合成的带有遗传信息的一类单链核糖核酸（RNA）。它在核糖体上作为蛋白质合成的模板，决定肽链的氨基酸排列顺序。mRNA存在于原核生物和真核生物的细胞质及真核细胞的某些细胞器（如线粒体和叶绿体）中。
RNA病毒和RNA噬菌体中的 RNA既是遗传信息的载体又具有mRNA的功能