Merge pull request AY2324S2-CS2103T-T08-2#249 from 0-yibai/ug-purpose

Add purpose section for user guide

docs/UserGuide.md

@@ -9,6 +9,18 @@ A warm welcome to all home bakers to our Strack.io User Guide! Strack.io is desi
 
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+## Purpose
+
+This User Guide serves both as a tutorial and as an instruction manual to our Strack.io application.
+To start learning using our app, you can take a look at the Quick Start section, and try out the different commands for yourself.
+If you are not sure about the format of any command, you can refer to the Features section for a detailed explanation.
+At the end of this User Guide, we have also provided a glossary of terminologies and a succinct list of commands for your easy reference during daily usage.
+
+As you read through this user guide, you will learn about:
+* How to use different commands provided by our app, illustrated by comprehensive examples
+* Constraints of input format in order for our app to run normally
+* Auxiliary capabilities of Strack.io application, including saving and exportation of data.
+
 ## Overview
 
 Strack.io is a **desktop app for home bakers to manage contacts of their customers, optimized for use via