Alzheimer's disease (AD) is one of the most common multifactorial diseases, including a range of abnormal cellular/molecular processes occurring in different regions of the brain. This disease is considered to be a major contributor to dementia in the elderly people. The pathophysiology involves accumulation of extracellular plaques containing the β-amyloid protein which is generated by the breakdown of the β-amyloid precursor protein (APP) in the brain. Another mechanism involves formation of intracellular neurofibrillary tangles of hyperphosphorylated tau protein. The AD can be classified into two types, familial AD (FAD) and sporadic AD (SAD) based on heritability apart from this the early-onset AD (EOAD) and late-onset AD (LOAD) forms are based on the age of onset. Some proteins, such as APOE, APP, BACE (b-amyloid cleaving enzyme), secretases, PS1/2 and tau proteins are reported in AD brain and have been correlated with disease. It is still unclear whether this disease comprises genetic or environmental factors or both. Many palliative drugs are available for the disease but there is still thirst for curative drugs with greater efficacy. It is required to understand the key factors involved in disease progression and their suitability as drug targets for discovering new drugs against Alzheimer's disease.