The point cloud template class pcl∷PointCloud<dataType> represents a cloud (basically a set of elements) of dataType values. For example, pcl∷PointCloud<pcl∷PointXYZRGB> is a cloud of points with xyz coordinates and RGB color values. There are a variety of ways to manipulate point clouds in the Point Cloud Library (PCL), which has a variety of methods for filtering, organizing, manipulating, and visualizing point cloud data, as well as for interfacing with input devices. A comprehensive tutorial/walkthrough on using point clouds can be found here (along with some instructions on using them with Kinect). A summary of using the point cloud data type with ROS can be found here.