Alzheimer’s disease (AD) is an irreversible, degenerative, and progressive neuronal disease leading to moderate memory impairment during its initial stages. The condition progressively damages memory and cognitive functions, resulting in diminished reaction of the patient toward the external atmosphere in the latter stages. According to the 2016 World Alzheimer Report, roughly 46.8 million individuals are globally afflicted with AD. The onset of symptoms is categorized as early-onset or late-onset AD. Patients with early onset typically have a non-memory phenotype characterized by visuospatial deficits. Early-onset autosomal dominant AD is linked to amyloid-β (Aβ) irregularities. Dementia is the chief characteristic of late-onset type. A recent study indicates that late-onset AD is characterized as a polygenic condition involving unusual interactions among various biological pathways. The primary risk factor for AD is age, succeeded by the cardiovascular and lifestyle-related risk factors, along with alterations that occur in the blood–brain barrier and cerebral vasculature. This chapter provides a comprehensive overview of the stages and progression of AD, emphasizing the biological, clinical, and epidemiological dimensions of the disease.