The document compares various region-based convolutional neural network (RCNN) techniques for classifying objects in images, including RCNN, Fast RCNN, and Faster RCNN. It first provides background on CNNs and how they are used for computer vision tasks like object recognition. It then describes the basic RCNN technique which uses selective search to generate region proposals that are input to a CNN for feature extraction and an SVM for classification. Fast RCNN improves on this by using a region of interest pooling layer to process features from the CNN in parallel rather than through separate layers. Faster RCNN introduces a region proposal network to generate proposals within the network to speed up processing. The techniques are implemented and evaluated on the CALTECH-101