RNA-seq is a high-throughput sequencing technique used to analyze the transcriptome of a biological sample. It allows researchers to quantify and identify all the RNA molecules in a given sample, providing valuable insights into gene expression, alternative splicing, and gene fusion events. RNA-seq has applications in various fields, including genomics, molecular biology, and bioinformatics, and has greatly advanced our understanding of gene regulation and expression patterns. It is a powerful tool for studying complex biological processes and diseases at the molecular level.