3D Slicer is an open-source software platform for medical image computing and visualization that allows users to load, segment, register, and analyze medical images from various modalities like MRI, CT, and DICOM. It provides tools for tasks such as interactive image segmentation, registration, visualization of diffusion tensor images and tractography, and integration of functional and anatomical data. Slicer has been used in applications such as surgical planning, virtual endoscopy, and pre-operative mapping of functional areas to avoid during surgery.