Snapshots are pre-releases of the ongoing development to minecraft, every Tuesday Dinnerbone announces the release of the Snapshot server
To play the latest snapshot you need to choose this in the server list in the Multicraft control panel.
- Click 'New Profile'
- Give the profile an name like "snapshot 14w21b"
- Check the box saying Enable experimental development snapshots then click 'save'
- In the Use version drop down choose the recent 'snapshot'
- Click Save Profile
- Choose the profile from the Profile drop down
- Put your username and password in and click 'Play'