For this particular tutorial, we will focus only on graphs in a grid. Usually, this is a 2D array, where you can hop from one cell to its neighboring cells. The best resource for this topic I think is from Indian Computing Olympiad Training Material: Reachability in a grid.

As always, feel free to post questions below if you get stuck of have doubts. And also, if you find good, but short, video tutorials, post those as well.