posts: User or community IDs and post IDs, separated by underscores. Use a negative value to designate a community ID.
extended: 1 - to return user and community objects needed to display posts, 0 - no additional fields are returned (default).
copy_history_depth: Sets the number of parent elements to include in the array copy_history that is returned if the post is a repost from another wall.
fields: List of comma-separated words
v: Version of API
Returns
Returns a list of post objects. If extended is set to 1, returns the following:
wall - Contains post objects.
profiles - Contains user objects with additional fields sex, photo, photo_medium_rec, and online.
groups - Contains community objects.
If the post is a copy of another post, returns an additional array copy_history with information about original posts.