Publish = appears on the public speakers and schedule pages once they are switched on. Contact details never leave the admin tool.
Click a cell to cycle Available, Not available, Unknown. Shift+click (or right-click) to add a note or mark it Locked in. Tick speakers in the header to highlight hours when everyone ticked is free.
Hard date (locked in)
Outside the times they gave, or not asked
Happy slot, plenty of other options
Happy slot, only a few other options
Happy slot, and it is their only one
Non-speaker item
Open slot (unfilled)