The article reviews the concept of visual working memory (VWM) and its capacity, which is strongly correlated with overall cognitive ability and can be measured using simple tasks. Recent studies have shown that VWM capacity influences various cognitive tasks, from saccade targeting to analogical reasoning. There is a debate over whether VWM capacity is limited by a discrete number of representations or by an infinitely divisible resource, but empirical evidence and neural network models currently favor a discrete item limit. VWM capacity varies significantly across individuals and groups, with some differences reflecting true storage capacity and others reflecting variations in memory efficiency. The article discusses the neural mechanisms underlying VWM, including the role of cell assemblies and oscillations, and highlights the importance of VWM in vision, such as in linking pre-saccadic and post-saccadic representations of objects. The nature of capacity limitations in VWM is explored, with evidence supporting both discrete slots and continuous resources models. Individual and group differences in VWM capacity are also examined, including the impact of factors like attentional processes and neural activity. The article concludes by emphasizing the importance of VWM in understanding broader cognitive functions and the potential for improving cognitive abilities through enhancing VWM capacity.The article reviews the concept of visual working memory (VWM) and its capacity, which is strongly correlated with overall cognitive ability and can be measured using simple tasks. Recent studies have shown that VWM capacity influences various cognitive tasks, from saccade targeting to analogical reasoning. There is a debate over whether VWM capacity is limited by a discrete number of representations or by an infinitely divisible resource, but empirical evidence and neural network models currently favor a discrete item limit. VWM capacity varies significantly across individuals and groups, with some differences reflecting true storage capacity and others reflecting variations in memory efficiency. The article discusses the neural mechanisms underlying VWM, including the role of cell assemblies and oscillations, and highlights the importance of VWM in vision, such as in linking pre-saccadic and post-saccadic representations of objects. The nature of capacity limitations in VWM is explored, with evidence supporting both discrete slots and continuous resources models. Individual and group differences in VWM capacity are also examined, including the impact of factors like attentional processes and neural activity. The article concludes by emphasizing the importance of VWM in understanding broader cognitive functions and the potential for improving cognitive abilities through enhancing VWM capacity.