Additive manufacturing (AM) technology, which has been under development for over 20 years, involves creating three-dimensional parts directly from CAD models by adding materials layer by layer. This process offers the ability to produce parts with complex geometries and materials that are not feasible with subtractive manufacturing methods. Significant progress has been made in the development and commercialization of new AM processes, and they have found practical applications in various fields such as aerospace, automotive, biomedical, and energy. The paper reviews the main AM processes, materials, and applications, and identifies future research needs. Key AM processes include Stereolithography (SLA), Fused Deposition Modeling (FDM), Selective Laser Sintering (SLS), Laminated Object Manufacturing (LOM), Three Dimensional Printing (3DP), and Laser Metal Deposition (LMD). These processes use materials like photo-curable resins, polyamides, wax, ABS, polycarbonate, metal/ceramic/polymer powders, and adhesive-coated sheets. AM technology significantly reduces lead times, is cost-effective for small batches, and can produce parts that are not possible with subtractive methods. Despite advancements, challenges remain, including limited materials, part accuracy issues, repeatability, and the lack of standardized processes. The paper also discusses the classification of AM processes based on the state of the starting material and provides an overview of the working principles of different AM processes.Additive manufacturing (AM) technology, which has been under development for over 20 years, involves creating three-dimensional parts directly from CAD models by adding materials layer by layer. This process offers the ability to produce parts with complex geometries and materials that are not feasible with subtractive manufacturing methods. Significant progress has been made in the development and commercialization of new AM processes, and they have found practical applications in various fields such as aerospace, automotive, biomedical, and energy. The paper reviews the main AM processes, materials, and applications, and identifies future research needs. Key AM processes include Stereolithography (SLA), Fused Deposition Modeling (FDM), Selective Laser Sintering (SLS), Laminated Object Manufacturing (LOM), Three Dimensional Printing (3DP), and Laser Metal Deposition (LMD). These processes use materials like photo-curable resins, polyamides, wax, ABS, polycarbonate, metal/ceramic/polymer powders, and adhesive-coated sheets. AM technology significantly reduces lead times, is cost-effective for small batches, and can produce parts that are not possible with subtractive methods. Despite advancements, challenges remain, including limited materials, part accuracy issues, repeatability, and the lack of standardized processes. The paper also discusses the classification of AM processes based on the state of the starting material and provides an overview of the working principles of different AM processes.