Let's start off by comparing the vertices of the triangles. In the first triangle, the point A is listed first. This corresponds to the point E on the other triangle. We know that these points match up because congruent angles are shown at those points. Listed next in the first triangle is point B. We compare this to point D of the second triangle. Again, these match up because the angles at those points are congruent. Finally, we look at the points C and F. The angles at those points are congruent as well.
We can also look at the sides of the triangles to see if they correspond. For instance, we could compare side AB to side ED. The figure indicates that those sides of the triangles are congruent. We can also look at two more pairs of sides to make sure that they correspond. Sides AC and EF have two tick marks each, which shows that they are congruent. Finally, sides BC and DF are congruent in the figure.