Intraplate volcanism - as the name suggests it is volcanism within the plates rather than at plate boundaries.
These are also known as hotspots.
Ocean island basalt (OIB) - is the basaltic rocks associated with intraplate volcanism.
Relation between mid-ocean ridges and hotspots:
Hotspot–ridge interaction produces a wide range of phenomena including excess crustal thickness, geochemical anomalies, off-axis
volcanic ridges, and ridge relocations or jumps.
For further study refer to this research paper.
A conceptual schematic of a ridge jump from that paper:
DR: Dying rift
PR: Propagating rift
There is a ridge jump towards the hotspot. Due to the ridge jump lithosphere from plate B is transfered to plate A.