Update README.md

README.md

@@ -1,5 +1,5 @@
-***After generating all VCF files you want to include in the panel,***
-***you can use bcftools-merge to merge them into a single Panel of Normal VCF.***
+The bcftools-merge is used to merge VCF files into a singe VCF.
+A common scenario is that after generating all VCF files you want to include in the panel, you can use bcftools-merge to merge them into a single Panel of Normal VCF.
 #### Usage
 ```bash
 # Enter the Choppy work environment