i hope i can make this make sense, if not let me know in the comments!
you use the “less than” sign to place ‘x’ between all numbers, meaning it could be any ‘real’ number.
we don’t use the equal sign underneath because there’s no reason; x can be equal to any number, so it won’t ever need to be equal to anything.
the interval notation places x anywhere between -infinity and +infinity because the arrows are pointed both directions horizontally, meaning that ‘x’ could be any number on the number line.