An end-effector is the part at the end of a robot arm that interacts with the world. On a humanoid, that might be a five-finger hand, a two-finger gripper, a suction cup, a tool mount, or a custom mechanism for one job.
Hands look more human, but they are expensive and difficult. Every extra joint adds motors, sensors, control complexity, failure points, and cost. A simple gripper can be less impressive on video and more useful in a warehouse.
This is why end-effectors reveal a company's real product bet. Dexterous hands imply a bet on general manipulation. Grippers imply a bet on specific industrial workflows. Tool mounts imply a bet that the robot is a mobile platform, not a human replacement.
When comparing humanoids, do not just ask whether the robot has hands. Ask what the end-effector can reliably pick up, how much force it can apply, whether it has tactile sensing, and whether the company has shown it working outside a staged demo.