update Troubleshooting.md (#107)

* update Troubleshooting.md

* update

README.md

@@ -113,6 +113,7 @@ If you have JAVA_HOME configured through the `maven.terminal.customEnv` setting,
 <details>
 <summary>Default Options for Maven Command</summary>
 The usage of maven executable is:
+
 > usage: mvn [options] [<goal(s)>] [<phase(s)>]
 
 You can use `maven.executable.options` to specify default **options** for all your maven commands executed in current project.

Troubleshooting.md

@@ -1,26 +1,30 @@
 # Troubleshooting
 
-## Requirements
-Please make sure Maven is either in the `PATH`, or that `maven.executable.path` is pointed to its installed location. Also make sure `JAVA_HOME` is specified either in environment variables or settings.
+## Backround knowledge
 
-### Available Maven executable
-By default, `mvn` command is executed directly in the terminal, which requires `mvn` can be found in system envronment `PATH`.
-If you do not want to add it into `PATH`, you can specify maven executable path in settings:
-    ```
-    {
-        "maven.executable.path": "/some-path-to-maven-home/bin/mvn"
-    }
-    ```
+### Where to find Error logs
 
-#### Possible error messages
+There are 2 types of command execution methods.
+* **Background command**. It spawn a child process in background for your commnad, and the process is showing in status bar. E.g. generating effective pom. You can find error logs in an `Output` panel named `Maven for Java`.
+* **Terminal command**. It sends plain text of your command to a terminal to execute. E.g. almost all the other maven comands. Error logs are directly printed in the corresponding terminals.
+  
+### Requirements
+
+* **Java**. Java Runtime is essential to run Maven commands.
+* **Maven / Maven Wrapper**. The extension actually leverages Maven executable file in your local machine. By default, it tries the following ones in order:
+  1. The absolute path specified in config `maven.executable.path` if it is not empty.
+  2. `mvnw` file under your workspace root folder. (If you prefer to bypass this one, you can change value of config `maven.executable.preferMavenWrapper` to `false`.)
+  3. `mvn` in your system's `PATH`.
+
+## Possible error messages
 Error message can be collected either **directly from the integrated terminal**, or **from `Maven for Java` output panel**.
+
 * Maven executable file not found/set.
     ```
     Command failed: mvn --version 'mvn' is not recognized as an internal or external command, operable program or batch file.
     ```
     In this case, please follow above instructions to set available maven executable path.
 
-
 * `M2_HOME` not correctly set.
     ```
     Error: Command failed: mvn help:effective-pom -f "xxxxxxxxxxxx\pom.xml" -Doutput="xxxxxxxxxxxxxxx\effective-pom.xml"
@@ -31,13 +35,10 @@ Error message can be collected either **directly from the integrated terminal**,
     ```
     In this case, please follow the error message to reset a correct `M2_HOME`.
 
-### Available Java Runtime (required by Maven)
-
-#### Possible error messages
 * `JAVA_HOME` not correctly set.
     ```
     The JAVA_HOME environment variable is not defined correctly
     This environment variable is needed to run this program
     NB: JAVA_HOME should point to a JDK not a JRE
     ```
-    In this case, please specify a correct JAVA_HOME environment variable, or re-install JRE/JDK if necessary.
+    In this case, please specify a correct `JAVA_HOME` environment variable, or re-install JRE/JDK if necessary.