Long non-coding RNAs (lncRNAs) are RNA transcripts longer than 200 nucleotides that play diverse functional roles in various biological processes. Classifying lncRNAs based on their genomic location, effects on DNA sequences, functional mechanisms, and targeting mechanisms is essential for understanding their roles and functions. This review summarizes the classification of lncRNAs according to these four major features. LncRNAs are categorized into intergenic and intronic types based on their genomic location. Intergenic lncRNAs are transcribed from non-coding regions between coding genes, while intronic lncRNAs are transcribed from introns of protein-coding genes. Sense and antisense lncRNAs are transcribed from the same or opposite strands of protein-coding genes, respectively. These classifications help in understanding their functional roles and interactions with other genes. LncRNAs can exert effects on DNA sequences through cis-acting or trans-acting mechanisms. Cis-lncRNAs regulate genes in close genomic proximity, while trans-lncRNAs regulate genes in distant locations. These mechanisms involve transcriptional interference, chromatin modification, and other regulatory processes. For example, Xist RNA regulates gene silencing on the X chromosome by recruiting the PRC2 complex. LncRNAs also function through various post-transcriptional mechanisms, including splicing regulation, translational control, and interaction with miRNAs. Some lncRNAs act as competing endogenous RNAs (ceRNAs), modulating miRNA activity. Additionally, lncRNAs can function as natural antisense inhibitors, promoting mRNA degradation. The targeting mechanisms of lncRNAs include acting as signals, decoys, guides, or scaffolds. These mechanisms allow lncRNAs to interact with proteins or RNA molecules to regulate gene expression. For example, HOTAIR functions as a guide to direct chromatin-modifying complexes to target genes. The classification of lncRNAs based on their length reveals that human lncRNAs are predominantly small (200-950 nt), while mouse lncRNAs are mostly medium (950-4,800 nt). This classification highlights the importance of considering species-specific differences in lncRNA studies. Overall, the classification of lncRNAs is crucial for understanding their functional roles and for further research into their mechanisms of action. Future studies should focus on exploring the evolutionary relationships between lncRNAs and small non-coding RNAs, as well as the functional significance of different lncRNA classes.Long non-coding RNAs (lncRNAs) are RNA transcripts longer than 200 nucleotides that play diverse functional roles in various biological processes. Classifying lncRNAs based on their genomic location, effects on DNA sequences, functional mechanisms, and targeting mechanisms is essential for understanding their roles and functions. This review summarizes the classification of lncRNAs according to these four major features. LncRNAs are categorized into intergenic and intronic types based on their genomic location. Intergenic lncRNAs are transcribed from non-coding regions between coding genes, while intronic lncRNAs are transcribed from introns of protein-coding genes. Sense and antisense lncRNAs are transcribed from the same or opposite strands of protein-coding genes, respectively. These classifications help in understanding their functional roles and interactions with other genes. LncRNAs can exert effects on DNA sequences through cis-acting or trans-acting mechanisms. Cis-lncRNAs regulate genes in close genomic proximity, while trans-lncRNAs regulate genes in distant locations. These mechanisms involve transcriptional interference, chromatin modification, and other regulatory processes. For example, Xist RNA regulates gene silencing on the X chromosome by recruiting the PRC2 complex. LncRNAs also function through various post-transcriptional mechanisms, including splicing regulation, translational control, and interaction with miRNAs. Some lncRNAs act as competing endogenous RNAs (ceRNAs), modulating miRNA activity. Additionally, lncRNAs can function as natural antisense inhibitors, promoting mRNA degradation. The targeting mechanisms of lncRNAs include acting as signals, decoys, guides, or scaffolds. These mechanisms allow lncRNAs to interact with proteins or RNA molecules to regulate gene expression. For example, HOTAIR functions as a guide to direct chromatin-modifying complexes to target genes. The classification of lncRNAs based on their length reveals that human lncRNAs are predominantly small (200-950 nt), while mouse lncRNAs are mostly medium (950-4,800 nt). This classification highlights the importance of considering species-specific differences in lncRNA studies. Overall, the classification of lncRNAs is crucial for understanding their functional roles and for further research into their mechanisms of action. Future studies should focus on exploring the evolutionary relationships between lncRNAs and small non-coding RNAs, as well as the functional significance of different lncRNA classes.