Check the picture below.
the hole on te red one, means that endpoint is not included in it, namely x = 1 is not part of it, namely x > 1, anything greater BUT not equals to "x".
likewise, the solid circle on the blue one means, that endpoint is included, namely x ⩽ 1, anything lesser than 1, including the x = 1 itself, so x = 1, x = 0, x = -1, x = -2.....
