This math topic focuses on understanding the domain and range of functions as illustrated on number lines, along with their verbal descriptions involving unions. Students will identify specific intervals from graphical representations (number lines) and choose the correct description of these intervals, including decisions on inequality symbols (less than, greater than, inclusive or exclusive). Problems include defining both domains and ranges from given number lines and varying their description through multiple choice answers. This requires comprehension of set notation and the ability to interpret graphical data.