Domain: possible x values (left to right)
Range: possible y values( down to up)
The domain is all the possible X Values.
Think if you were to drag your pencil right or left are there points where the graphs stops. At times you will have a domain that extends to infinity, you can have a domain like
The range is all the possible Y values, as if moving your pencil up and down.
With domains and ranges there is also certain notation.
The range for this would be
The domain would be
An example with hard brackets would be a square root function where all of the values need to be + inside for example