Optical coherence tomography angiography (OCTA), derived from optical coherence tomography (OCT) technology, is a vascular imaging approach that leverages flowing red blood cells as an intrinsic contrast agent. It has key advantages, including high resolution, sensitivity, and noninvasiveness. By discerning the amplitude and phase variances within OCT signals between flowing red blood cells and stationary tissue, OCTA enables 3D imaging of the retinal vascular network. Leveraging vascular density, diameter, perimeter, and complexity indices, OCTA is a screening tool for ocular pathologies such as diabetic retinopathy (DR) and venous occlusion (VO), exhibiting notable efficacy in clinical interventions. This article provides an overview of the evolution of OCTA, elucidates its algorithmic fundamentals, delineates clinical quantitative metrics, and briefly evaluates the comparison between various OCTA methods and standard quantitative indicators.