3 Answers

I know it’s late, but this might be helpful to others….
Set Builder Notation: Because x ≤ 14 is an inequality with infinitely many solutions and is not itself a set of solutions, a notation called Set Builder Notation has been devised for writing solutions to an inequality as a set. For example, the solution set consisting of “all real numbers x such that x is less than or equal to 14,” can be written as {x l x ≤ 14}. The vertical line segment ” l ” is read, “such that”.

I don’t recognize it from algebra, but in statistics,  means ‘given that’ – P(AB) is the probability that event A happens given that event B happens. It is therefore defined as the number of times B intersects (is true as well as) A out of all the number of times A is true.
I would ignore the x’s and go back looking for the  operator. It means something else in computer programing, and might also be used in logic.