They go on and on

Question

What's the 4-word phrase I'm looking for?

---

 E S N F J A
 L M N U L G
 D I X Z E A
 I V A C Y S
 P D W N O M
 O L I O A L

Why is...

x: 5th

x+2: 2nd

x+3: 3rd

x+5: 1st

x-3: 3rd

x: 1st

x-2: 2nd

x: 3rd

x+1: 1st

x-5: 1st

x: 6th

x+2: 3rd

x-1: 4th

---

Note: The knowledge needed is very basic. I'm sure most of you don't need google to solve this puzzle.

Answer 1

The answer phrase is:

Lines on a plane

Which can be obtained by noting that

"Why is..." actually means "y=..." which can be composed with the left side of each colon to make the formula of a line. For example, the first one would become "y=x" (5th). If we consider the black dot as the origin (0,0), and we plot each line, we'll notice that they all are parallel to y=x. Then we can pick the nth letter for that line inside the grid (corresponding the grid with the letters below), to extract.

This would look like this for the first letter:

which corresponds in the letter grid with the

L in row 2 column 5.