In our previous Sprint we had a Product Backlog item that we simply did not know enough about to accept in to the Sprint. In response to this challenge we adopted a Spike task. The point (no pun intended) of a Spike is to focus attention on gathering information.

The Spike task was time limited to two days and was in this case completed early. Enough information was gathered to allow the Product Backlog Item to be broken down in to Sprint Backlog Items and added to the next Sprint.

Spikes are handy if there is a requirement to provide answers to a business related or technical question and they also have a cool name.

Discussion on Spikes and Tracer Bullets (used in XP):