Just think of what the url is. If you are submitting to a https then it is secure, if it is http then it is not.
Basically, when you submit
https://www.mysite.com... the following occurs:
1. Client establishes a tcp connection to port 443 (the standard port for https).
2. Both client/server exchange information - where protocol,cipher and certificate information is exchanged.
3. Encrypted request sent to server.
4. Encrypted response sent to client.
5. Close ssl/tcp connection.