Refers to a road or path on a slope, whether going up or down. Can be used for both gentle and steep inclines.
この坂道を登ると、駅に出ます。
If you go up this hill road, you'll reach the station.
雨の日は坂道が滑りやすくなる。
On rainy days, slopes become slippery.
I climb this slope every morning on my way to school.
Going downhill on a bicycle is dangerous.
There's a steep slope ahead.
The slope continues all the way from the station to my house.