The globalization process has facilitated the introduction of non-native plant species into novel ecosystems, leading to a marked increase in invasive alien plants (IAPs) that pose a serious threat to native biodiversity and ecological systems. While earlier research has extensively investigated the challenges posed by IAPs, there is a growing interest in explaining the fundamental mechanisms that propel certain non-native plants toward invasiveness. This chapter aims to comprehend the factors that determine the success of certain non-native species in colonizing and dominating new ecosystems. It explores the ecological theories that underpin invasion ecology and analyzes the adaptive strategies of IAPs, notably the Competitive, Stress-tolerant, and Ruderal (CSR) strategies. The chapter discusses how invasive species possess specific traits that enable them to adapt and thrive in new environments, often outcompeting native species. The ecological strategies of these plants, including Grime’s CSR strategies, are analysed to understand their success in various environments. Many hypotheses have been developed to explain the success of invasive plants, including the enemy release hypothesis, fluctuation resources hypothesis, novel weapons hypothesis, evolution of increased competitive ability (EICA) hypothesis, and the rapid evolution hypothesis. IAPs must overcome multiple barriers to progress along the introduction-naturalization-invasion continuum and become dominant in their introduced ranges. While inherent traits are important, propagule pressure and residence time are more important in determining invasion success. A significant focus is placed on propagule pressure and its role in the establishment and spread of invasive species. Case studies, such as the one from South Africa’s Agulhas Plain, are used to illustrate the impact of propagule pressure on invasion patterns. The chapter also addresses the role of environmental factors, including disturbances and climate, in facilitating plant invasions. IAPs achieve dominance in introduced ranges through complex interactions between inherent traits, rapid evolution, disturbance regimes, resource availability, biotic interactions, and introduction dynamics. Generalizing determinants requires comparing native and introduced ranges within a framework that captures the context dependencies of plant invasions. Finally, the chapter presents a comprehensive overview of the implications for conservation and management. It emphasizes the need for early detection, risk assessment, public education, integrated management approaches, adaptive management, collaborative efforts, and ongoing research and monitoring to effectively manage and mitigate the impact of invasive plant species on ecosystems. This chapter provides a detailed and research-based exploration of the journey of plant species from being exotic/aliens to becoming invasive, offering insights into their ecological impacts and the strategies required for effective management and conservation.