I'm fairly new at computer vision and I've read an explanation at a medium post, however it still isn't clear for me how they truly differ.
- Object Detection : is the technology that is related to computer vision and image processing. It's aim? detect objects in an image.
- Semantic Segmentation : is a technique that detects , for each pixel , the object category it belongs to , all object categories ( labels ) must be known to the model.
- Instance Segmentation : same as Semantic Segmentation, but dives a bit deeper, it identifies , for each pixel, the object instance it belongs to.
Here's an example of the main difference.
In the second image where Semantic Segmentation is applied, the category ( chair ) is one of the outputs, all chairs are colored the same. In the third image, the Instance Segmentation, goes a step further and separates the instances ( the chairs ) from one another apart from identifying the category ( chair ) in the first step.
Hope this clears it up for you a bit.