Forest fires represent a significant environmental and socio-economic challenge, driven by the complex interplay of climatic, topographic, and anthropogenic factors. Many studies have utilised a wide range of fire-influencing variables, such as temperature, precipitation, wind speed, elevation, and others, to model fire susceptibility maps and develop predictive models. However, these studies often assume that readers are already familiar with the underlying mechanisms that link these factors to fire occurrence, without providing detailed explanations of how each variable contributes to ignition probability and fire spread. This paper aims to address this gap by offering an accessible and comprehensive synthesis of key variables influencing forest fire susceptibility. Based on findings from previous systematic reviews and recent literature, 22 critical fire factors are categorised into three groups: climatic and environmental factors, topographic variables, and anthropogenic influences. For each factor, intuitive explanations of its relationship with fire occurrence are provided to guide hypothesis-driven feature selection for fire mapping and modelling. Crucially, this review emphasises that while these factors are globally prevalent, their application requires statistical validation to account for regional differences in fire regimes. By clarifying the mechanisms behind fire-influencing factors, this review supports more robust fire risk assessments and informs evidence-based strategies for wildfire prevention and management.