Messaging Activity pops up along with mail application in Android

Question

I wrote an email application in Android , that uses Action_SEND intent. When I call startActivity(i); where i is intent, along with email Application , messaging application is also popping up. But when I wrote an application for email why should messaging application also should pop up. can I be explained clearly regarding this concept.

Intent sendIntent = new Intent(Intent.ACTION_SEND);
String[] mailto = recipients;
sendIntent.putExtra(Intent.EXTRA_EMAIL, mailto);
String[] mailCc = recipientsToBeCopied;
sendIntent.putExtra(Intent.EXTRA_CC, mailCc);
String[] mailBcc = recipientsToBeBlindCopied;
sendIntent.putExtra(Intent.EXTRA_BCC, mailBcc);
String subject = strSubject;
sendIntent.putExtra(Intent.EXTRA_SUBJECT, subject);
String body = strBody;
sendIntent.putExtra(Intent.EXTRA_TEXT, body);
sendIntent.setType("text/plain");
startActivity(Intent.createChooser(sendIntent, "send mail.."));

Can any one tell me reason for using createChooser of intent and also reason for this application popping up messaging activity.