What is the difference between "intraphoton" and "interphoton" entanglement?

Intraphoton entanglement uses the degrees of freedom from one photon only to create entanglement. So, here either polarization and linear momentum or polarization and angular momentum can be used to create entanglement. Interphoton entanglement is the entanglement created between 2 spatially separated photons. So, naturally latter is less stable than former. For this reason, this paper used former as a resource to create latter.