diff --git a/README.md b/README.md
index c99c441..994183c 100644
--- a/README.md
+++ b/README.md
@@ -1,11 +1,21 @@
-# What is Regular Expression?
+## What is Regular Expression?
-Regular expression is a group of character or symbols which is used to find a specific pattern from a text.
-The word "Regular expression" is a mouthful, you will usually find the term abbreviated as "regex" or
-"regexp". Regular expression is used for replacing a text withing a string, validating form, extract a substring
-from a string based upon a pattern match, and so much more.
+> Regular expression is a group of characters or symbols which is used to find a specific pattern from a text.
-# Table of Contents
+A regular expression is a pattern that is matched against a subject string from left to right. The word "Regular expression" is a
+mouthful, you will usually find the term abbreviated as "regex" or "regexp". Regular expression is used for replacing a text withing
+a string, validating form, extract a substring from a string based upon a pattern match, and so much more.
+
+Imagine you are writing an application and you want to set the rules when user chosing their username. We want the username can
+contains letter, number, underscore and hyphen. We also want to limit the number of characters in username so it does not look ugly.
+We use the following regular expression to validate a username:
+
+
+
+Above regular expression can accepts the strings "john_doe", "jo-hn\_doe" and "john12\_as". It does not match "Jo" because that string
+contains uppercase letter and also it is too short.
+
+## Table of Contents
1. [Basic Matchers]()
2. [Meta character]()
@@ -19,17 +29,16 @@ from a string based upon a pattern match, and so much more.
## 1. Basic Matchers
-
-A regular expression is just a pattern of letters and digits that we used to search in a text. For example the
-regular expression `cat` means: the letter `c`, followed by the letter `a`, followed by the letter `t`.
+A regular expression is just a pattern of letters and digits that we used to search in a text. For example the regular expression
+`cat` means: the letter `c`, followed by the letter `a`, followed by the letter `t`.
"cat" => The cat sat on the mat
-The regular expression `123` matches the string "123". The regular expression is matched against an input string
-by comparing each character in the regular expression to each character in the input string, one after another.
-Regular expressions are normally case-sensitive so the regular expression `Cat` would not match the string "cat".
+The regular expression `123` matches the string "123". The regular expression is matched against an input string by comparing each
+character in the regular expression to each character in the input string, one after another. Regular expressions are normally
+case-sensitive so the regular expression `Cat` would not match the string "cat".
"Cat" => The cat sat on the Cat
@@ -37,8 +46,9 @@ Regular expressions are normally case-sensitive so the regular expression `Cat`
## 2. Meta Characters
-Meta characters are the building blocks of the regular expressions. Some meta characters have a special meaning
-that are written inside the square brackets. The meta character are as follows:
+Meta characters are the building blocks of the regular expressions. Meta characters do not stand for themselves but instead are
+interpreted in some special way. Some meta characters have a special meaning that are written inside the square brackets.
+The meta character are as follows:
|Meta character|Description|
|:----:|----|
@@ -57,9 +67,9 @@ that are written inside the square brackets. The meta character are as follows:
## 2.1 Full stop
-Full stop `.` is the simplest example of meta character. The meta character `.` matches any single character. It
-will not match return or new line characters. For example the regular expression `.ar` means: any character,
-followed by the letter `a`, followed by the letter `r`.
+Full stop `.` is the simplest example of meta character. The meta character `.` matches any single character. It will not match return
+or new line characters. For example the regular expression `.ar` means: any character, followed by the letter `a`, followed by the
+letter `r`.
".ar" => The car parked in the garage.
@@ -67,10 +77,9 @@ followed by the letter `a`, followed by the letter `r`.
## 2.2 Character set
-Character sets are also called character class. Square brackets are used to specify character sets. Use hyphen
-inside character set to specify the characters range. The order of the character range inside square brackets
-doesn't matter. For example the regular expression `[Tt]he` means: an uppercase `T` or lowercase `t`, followed by
-the letter `h`, followed by the letter `e`.
+Character sets are also called character class. Square brackets are used to specify character sets. Use hyphen inside character set to
+specify the characters range. The order of the character range inside square brackets doesn't matter. For example the regular
+expression `[Tt]he` means: an uppercase `T` or lowercase `t`, followed by the letter `h`, followed by the letter `e`.
"[Tt]he" => The car parked in the garage.
@@ -78,9 +87,9 @@ the letter `h`, followed by the letter `e`.
### 2.2.1 Negated character set
-In general the caret symbol represents the start of the string, but when it is typed after the opening square
-bracket it negates the character set. For example the regular expression `[^c]ar` means: any character except
-`c`, followed by the character `a`, followed by the letter `r`.
+In general the caret symbol represents the start of the string, but when it is typed after the opening square bracket it negates the
+character set. For example the regular expression `[^c]ar` means: any character except `c`, followed by the character `a`, followed by
+the letter `r`.
"[^c]ar" => The car parked in the garage.
@@ -89,8 +98,8 @@ bracket it negates the character set. For example the regular expression `[^c]ar
### 2.2.2 Repeating character set
-We can repeat a character class by using `+`, `*` or `?` operators. For example the regular expression `[a-z]+`
-means: any number of lowercase letters in a row.
+We can repeat a character class by using `+`, `*` or `?` operators. For example the regular expression `[a-z]+` means: any number of
+lowercase letters in a row.
"[a-z]+" => The car parked in the garage.