security - IPSec vs OpenSSL vs PGP -

ipsec employed @ ip level, ssl @ transport level , pgp @ application level. in lecture not says:

ipsec: general solution least flexible ssl: still general , flexibility pgp: least general flexibel.

i guess general refers kind of protocol can secure. ipsec can secure uses tcp or udp. pgp least general because encrypts emails , therefore specific. understanding right?

however have no idea flexibilty refers in context, idea? has extensibility?

thanks

ipsec: internet layer protocol, means runs above ip layer, such tcp or udp example, or other newer protocol, encrypted ipsec. however, protocol encryption/authentication of packets/protocol above , this, less flexible in some sense compared other 2 still flexible if need network encryption.

ssl: encryption protocol, similar (i guess) ipsec, operates @ higher layer ipsec. operates on application layer means protocol runs on top of tcp, udp, etc...

now 1 problem ipsec flexible in respect in lower in network layer, poses problem in devices needs support ipsec protocol itself, , cheap consumer routers don't. in sense ssl more flexible ipsec because operates on higher layer.

pgp: different domain ssl/ipsec, because ssl/ipsec restricts their-selves network encryption, don't deal encryption of files or other data, deal encryption of "bytes" going on network , once other end has read in bytes going sitting there unencrypted.

now pgp application/standard can use encrypt files destination public key , destination's private key can decrypt file. anyway can encrypt file, email, or ever transport on network destination , achieve same thing. on other hand can store file on disk encrypted or copy external harddrive example, , walk down hallway , give destination.

so in summary ipsec/ssl equivalent, run on different network layers, , pgp entirely different domain ipsec/ssl can still use pgp encrypt piece of data , transfer on network.

so in sense of flexibility, in pgp context in can use other things such storing encrypted files on disk, or can use private key sign piece of documentation/file , can use public key prove came you.