A Start Space is a kind of Space that appears in a few games.
They first appear in the game Super Mario Bros. 3, where they are referred to as Start Panels. Here they are white squares with the word START on them. They appear at the beginning of each World. Mario and Luigi start on them, and get thrown back to the start place when they die in the first level of the game, or get a Game Over. Sometimes, mini-game markers appear on the Start Space, as it is possible of all other spaces on Super Mario Bros. 3 maps. In Super Mario World, Yoshi's House could be considered a Start Space of sorts, as Mario begins here.
Start Pads return in New Super Mario Bros., where they serve as the start of the game as well, but are now black circles with red arrows.
The Start Space as seen in Mario Party 4. Here, there is a lottery going on.