Please help having a hard time understainding this. Describe what the graph of interval [-4, 10] looks like. Is it a solid dot at -4, a solid dot at 10 and a heavy line that connects to the two. The dots are solid as there is a square bracket at the ends of the interval.

You are correct, you would put a dot at both ends of the interval to indicate that -4 and 10 are included in the interval.

[-4 , 10] can also be written

If the question was (-4, 10) then the round brackets indicate that -4 and 10 are not included and your graph would have open circles (instead of dots) at -4 and 10.

(-4 , 10) can also be written

These can be combined. If you wanted to include -4 but not 10 it would be [-4, 10) which would give you a dot at -4 and an open circle at 10.