This chapter aims to encapsulate recent findings regarding long non-coding RNAs (lncRNAs), highlighting their inherent potential as molecular biomarkers, diagnostics, and therapeutics in the treatment of human diseases. With advancements in sequencing technologies, the exploration of lncRNAs presents a frontier laden with unknowns. Initially, the ongoing refinement and expansion of lncRNAs’ definition and categorization reflect their complex and varied nature. Subsequently, diverse methodologies and approaches have been devised to elucidate lncRNA characteristics, encompassing identification of new types, subcellular localization studies, functional analyses, molecular interactions, and bioinformatics assessments. Furthermore, the current basic research has illuminated the operational mechanisms of lncRNAs, which involve intricate networks of interactions with DNA, RNA, and proteins in the cell. Moreover, lncRNAs are indicated to assume critical roles in embryonic development and organ differentiation. Understanding the basics of lncRNA would help us develop more intricate RNA-based medicine for human diseases.