I think, maybe, you're talking about "interval notation" and "set builder notation". Let's see if I can explain.
If you want to graph all the elements between and including 1 and 4, we can write the solution set in two ways.
Interval Notation: [1, 4]
The brackets mean the endpoints are included in the graph. Had they not been included, we would have used parentheses.
Set Builder Notation:
This is read "The set of all x, such that x is greater than or equal to 1 and less than or equal to 4".
Does this help? If not, post specific examples.