Before going through this lesson, I've only encountered graphs in a Data Structures and Algorithms course I took a while ago. I was aware that graphs were discrete structures consisting of vertices and edges that connect these vertices. But I have never really dived deep into their different types and real-world applications. It was only when I studied this week’s lesson that I realized how ubiquitous graphs really are in our digital world.

 The types of graphs are as follows:

1. Simple graph
2. Multigraph
3. Pseudograph
4. Directed graph
5. Directed multigraph

 Regardless of which type of graph we are dealing with, roads between cities are used as the prime example of real-world application of graphs. It just takes a certain level of understanding to identify which type of graph one should use, as established in the week’s Problem Set. I can imagine how Google Maps is implemented as a large graph of every street as an edge and every destination as a vertex. I also assume that its direction-finding feature is based on a Shortest-Path finding algorithm similar to Dijkstra's algorithm.

 I find that from video games to web-based networks, the possibilities are certainly endless with the applications of this abstract concept. Even the search engine for Google itself was once based on a network of interconnected hyperlinks modeled as graphs. I look forward to creating meaningful programs that utilize graphs and their unique properties. Such possibilities, especially in this era of Artificial Intelligence and Quantum Computing, makes Computer Science a very exciting field to be involved in.