diff --git a/5-Add-virtual-motors.md b/5-Add-virtual-motors.md
index 639d65647d94a93a751beaec91f2f1ede2eb86e5..995c889d8094efae8f8022c25ab3aded32a5ed2c 100644
--- a/5-Add-virtual-motors.md
+++ b/5-Add-virtual-motors.md
@@ -234,6 +234,19 @@ make[1]: Leaving directory '/home/beams/USERNAME/PET-S2/epics/synApps_6_2_1/ioc/
 ```
 $ ldd bin/${EPICS_HOST_ARCH}/xxx | grep vmc
 ```
+<details>
+<summary>what does this mean?</summary>
+
+The command `ldd bin/${EPICS_HOST_ARCH}/xxx | grep vmc` is used to determine if the **xxx** binary executable file in the **bin/${EPICS_HOST_ARCH}** directory has a dynamic dependency on any shared libraries containing the string "vmc" in their names. Here's what the command does:
+
+- `ldd` lists the dynamic dependencies of a binary executable file. It shows the shared libraries that the executable requires to run successfully.
+- `bin/${EPICS_HOST_ARCH}/xxx` specifies the path to the **xxx** binary executable file.
+- `| grep vmc`: 
+  - the `|` symbol is a pipe operator that redirects the output of the `ldd` command to the next command in the pipeline.
+  - `grep vmc` is a command that searches for the string "vmc" in the output of the previous command (`ldd` in this case). It filters the output and displays only the lines that contain the string "vmc".
+
+</details>
+
 <details>
 <summary>output</summary>