Key transport vs key encapsulation? What exactly is the difference between key transport and key encapsulation? Either they seem to be used interchangeably, either I'm mixing stuff up.
Key encapsulation or key wrapping is the encryption of a key with another key. There may be a symmetric key or asymmetric key pair that encapsulates the key destined for transportation; this key can then be called a key transport key.

Key transportation is simply the secure transportation of a key. For public keys you'd expect integrity and authenticity - so that the receiver can trust the public key to have been sent by the right entity. Secret keys require confidentiality as well - which is why they are commonly encapsulated. Private keys would also require confidentiality of course, but generally you should not transport private keys at all - they're private: not to be shared.

Commonly I'd expect encapsulation / wrapping to be used for secret keys for secure transport. It is however perfectly possible to secure them otherwise (diplomatic post with a USB-thumbstick for instance).

Key encapsulation &amp; transport is just one way of establishing keys between two or multiple parties. Another way would be (authenticated) key agreement, key sharing schemes and so on.