In the game of "Life", the objects die. Objects can also be "born." For an object to be born, there needs to be an empty cell on the game area. For "Life" to be realistic, we also say that an empty cell needs a "family" from which it is created. So, an empty cell with a certain number of neigbors (adjacent cells which contain objects) will turn into a non-empty cell.
For example, if you choose a "families" value of 3, an empty cell will gain a "newborn" (a new object) if it has exactly 3 neighbors.