The low dropout regulator (LDO) is a key component in power management, providing an accurate and stable output voltage against line/load variations and power supply ripple. From a literature review, we found that conventional analog and digital LDOs still exhibit difficulties to achieve good transient response or power supply rejection under certain scenarios. Therefore, it is straightforward to combine them as a hybrid LDO, enjoying the benefits of both topologies. Then, we can classify the hybrid LDO as analog-assisted-digital (AAD) and digital-assisted-analog (DAA). This brief reviews comparatively previous works on AAD and DAA LDOs, summarizes their pros and cons, and discusses possible application scenarios.