(Ignore the equations and numbers and other triangle diagram, they were from later in class)
Angles of elevation and angles of depression are formed from a line of sight and a horizontal line. Angles of elevation are formed when the line of sight is going up from the horizontal, angles of depression are formed when the line of sight is going down from the horizontal. Important: Angles of depression are not formed between the line of sight and the vertical!
Also note: Within the same diagram, referencing the same line of sight, an angle of elevation and an angle of depression are alternate interior angles, and the horizontal lines are parallel, so they are congruent. (Note the arc marks in the above diagrams).
From here, we worked on this worksheet: Angles of Depression and Elevation
The hardest part is often making an accurate diagram. Really think carefully about where an angle goes (especially for angles of depression!). Also for lengths given, consider whether or not it makes sense for them to be the line of sight, horizontal, or vertical.
When I say I am 10 feet away from a wall, that distance is not vertical, and it is not angled up from my feet towards the top of the wall! That distance is measured along the ground, horizontally, perpendicular to the wall.