GCM SENDER is sender id which can be retrieved on Google API Console, like "AIzaSyDAYveZOAwO9XSdbipu4hER5wt8I_afrIY".
GCM CLIENT is client id which is given when you register your Android app on GCM server, like "APA91bGQ3i3wdDbsEaKXkykQwxD1UmxlsIa8kxOGcV03I5ALr73spLpGJrjQk-gWqVw2VdZWULp95e4tT5dJvUTpVfPHSv4KllLxWpWOHJkHjsVQ92arMXBy43o6twUjUOBjBpEcORWxYwMCBtounjs87lhyAy6nnkfM0q2ePhLXw1t6m3kMRNw "
Parameters are pairs of two strings, key and value, which will be delivered as payload along GCM message itself.
