Update the summary section (WIP)

Author: hristog

diff/index.md

@@ -119,7 +119,7 @@ This automatically means that we wouldn't want to be considering matching blocks
 
 This particular representation is also referred to as _unified format_, in the context of the GNU `diff` tool, and that was the relevance of the `-u` command-line argument  in the opening paragraph (alternatively accessible via the `--unified` flag). Some alternative representations, which we won't be discussing in this chapter are the _normal format_ (`--normal`) and _context format_ (`-c` or `--context`). They're closely related and are possible to be derived - with relatively minor modifications - using the approaches which we'll get acquainted with in this chapter. Naturally, for further details and even more possible representations, you're welcome to refer to GNU `diff`'s `man` pages.
 
-Let's step back a bit and try to think in what domains we'd expect the kind of algorithms that we need in this case to originate. Given two or more sequences of comparable-for-equality items, it is of interest to identify the longest possible subsequences of items which are equal between the sequences under consideration.
+Let's step back a bit and try to think in what domains we'd expect to see applications of the kind of algorithms are relevant to our use case. Given two or more sequences of comparable-for-equality items, it is of interest to identify the longest possible subsequences of items which are equal between the sequences under consideration.
 
 - For instance, in bioinformatics and molecular biology, DNA sequences can be represented via the symbols A, C, G and T which correspond to the four nucleobases, associated with DNA molecules, namely adenine, cytosine, guanine and thymine. One possible use-case is comparison between DNA sequences for the purpose of capturing some notion of similarity, for instance, with respect to a new DNA sequence. Then, one form of a similarity metric is finding the longest common subsequence between the input sequences.
 - In computational linguistics, two strings may be compared for similarity in multiple ways, and the longest common subsequence is one way of solving the approximate string matching problem.
@@ -573,9 +573,12 @@ $ git difftool HEAD~..HEAD
 
 ## Section N.7: Summary
 
-```
-TODO: Summary.
-```
+[Figure N.M](#figure-n-m-summary) summarizes the key ideas introduced in this chapter.
+
+<p align="center">
+<a id="figure-n-m-summary"><img src="" alt="TODO: Add image." /></a><br />
+Figure N.M: A diff tool concept map.
+</p>
 
 ## Section N.8: Exercises