Added session types warning

docs/design-phase/step.md

@@ -217,6 +217,16 @@ he is using, the *use_any_session_to_target* parameter can be used.
     ...
 ```
 
+!!! warning "Session types"
+
+    Metasploit Framework supports two types of sessions.
+    
+    The first is a shell session, you can run any shell commands you want.
+    
+    The second is called Meterpreter. It allows you to use it's provided commands, such as `ifconfig` or `sysinfo`. 
+    To run a command in a shell, you need to use the `execute` command with the `-f`, `-i`, and `-a` options (`execute -f <command> -i -a <arguments>`).
+    In some cases, the command execution can fail. Before creating a plan, make sure it works for your target system/exploit.
+
 ## Output sharing
 Output sharing is used for sharing gained data (*serialized_output*) between multiple steps. To go through the data we use a modified 
 version of a dot notation.