How can you blur background in photo while keeping foreground sharp?

To blur the background while keeping the foreground sharp, you can use a shallow depth of field by selecting a wide aperture (a low f-stop number) on your camera. This technique creates a focus on the subject in the foreground, while the background becomes increasingly blurred. Alternatively, you can achieve this effect in post-processing using photo editing software, where you can apply a blur effect selectively to the background. Additionally, using a longer focal length or getting closer to your subject can enhance the background blur.