There are two main ways to blur a background in Photoshop:

1. Using the Blur Gallery:

   1. Open the image in Photoshop.
   2. Go to Filter > Blur Gallery.
   3. Choose a blur filter from the list. Some popular blur filters include:
      • Field Blur: This blur filter creates a natural-looking blur that is similar to the blur created by a camera lens.
      • Iris Blur: This blur filter allows you to create a vignette effect, with a sharp subject in the center of the image and a blurred background.
      • Tilt-Shift Blur: This blur filter creates a miniature effect, with the image appearing to be a miniature model.
   4. Adjust the blur settings to your liking.
   5. Click OK to apply the blur filter.

2. Using a layer mask:

   1. Open the image in Photoshop.
   2. Duplicate the background layer by pressing Ctrl/Cmd + J.
   3. Select the Quick Selection Tool (W).
   4. Select the background of the image.
   5. Press Ctrl/Cmd + Shift + I to invert the selection.
   6. Press Ctrl/Cmd + J to create a new layer from the selection.
   7. Apply a blur filter to the new layer.
   8. Use a layer mask to adjust the blur effect. To do this, select the layer mask and use a black brush to hide the blurred background and a white brush to reveal the blurred background.

Which method you choose to blur a background in Photoshop depends on your personal preference and the desired effect. The Blur Gallery is a good option for creating a natural-looking blur, while using a layer mask gives you more control over the blur effect.