Telomerase is an inverse transcriptase enzyme with an RNA template, which prevents the critical shortening of the ends of the chromosomes. This non-systematic review document presents and analyses the biological role of telomerase with regards to the length of the telomeres, highlighting its importance for chromosomal content homeostasis, the regenerating ability of stem cells, regulation of the mitochondrial function, the development of tumors and other pathologies, and premature aging. Furthermore, another pathway was described for maintaining telomere length that is also related to carcinogenesis. The conclusion is that despite the results obtained through different animal experiments showing alternative therapeutic applications, it is still necessary to further investigate the molecular mechanisms of telomerase.