Plant endophytes are thought to represent new sources of naturally occurring substances that have a range of biological effects, such as antibacterial, anti-inflammatory, anticancer, herbicidal, antileishmanial, and antioxidant properties. Numerous strains have been reported to produce a wide range of specialized products, including terpenoids, alkaloids, polyketides, phenolic compounds, coumarins, and quinone derivatives. Various plant-microbe relationships have an impact on the environment and agriculture. The ability to create a wide range of proteins and metabolites has been developed by both plants and microorganisms to facilitate or regulate their interactions with other organisms and alter their environmental conditions. A number of these high-value metabolites that endophytes produce have found extensive usage in medicine and other socioeconomic fields. Quick progress in the field of genomics has made it possible to unravel the biology and ecology of endophytes, including their potential for metabolism, by analyzing their genetic blueprints and examining the ways in which they carry out particular tasks in diverse ecological and environmental settings. In this article, we examine current developments in our knowledge of the biology and ecology of endophytes and how these discoveries have been applied to promote environmentally friendly farming practices, create novel medicinal metabolites, and enhance environmental health. Advances in gene modification technologies and a deeper understanding of endophyte biology have led to the promise that endophytes can be genetically engineered to produce “value-added” compounds and be used to address environmental and agricultural issues. To reach their full potential, endophyte biology still has a few knowledge gaps that need to be filled.