utility descriptions written

doc/crest-cmd-user-guide.md

@@ -4,7 +4,7 @@
 - [I. Description](#i-description)
 - [II. Technical Questions](#ii-technical-questions)
 - [Appendix 1: Supported Commands](#appendix-1-supported-commands)
-- [Appendix 2: The Utilities](#appendix-2-the-crestimport-and-crestexport-utilities)
+- [Appendix 2: The Utilities](#appendix-2-the-utilities)
 
 ---
 
@@ -146,6 +146,8 @@ To get a short help for the each utility you can use the flag -h or --help. For
 ```bash
 ./copyGlobalTag -h
 ```
+Below we use `CREST_SERVER` as an environment variable with the server URL, like `http://crest-04.cern.ch:80` for example.
+You should carefully select the server you are going to use.
 
 ### 1) crestExport
 crestExport is an utility to make a dump of a tag and the tag data (i.e. the tag meta info, IOVs and payloads) from the CREST server to the file storage.