Java Security

Hi! I've done a crypt/decrypt application which use a certificate generated with the keytool tool (using RSA). �What is the difference using that kind of certificate vs using the keypair generator? �how it is used the keypair generator? and �for what use/purpose one must use keypair generator)

What I'm doing is crypting a file and send it over the network. Later, download it, decrypt it and read it.

Thanks a lot for your guidance!