If the dressed avatar includes shoes, a saved snapshot also includes the shoes. For example, you can have multiple snapshots, each with its own shoes.
If you share a BW file with shoes that has been saved as Garment + Avatars & Accessories (*.bw), this allows the other user to view and adjust the shoes. If a user opens such a BW file containing shoes, the shoes are automatically added to the user’s closet.
For more information about the file format, refer to Opening and Saving a BW File.