From a tactical perspective, that means this can interact with basically any other satellite.
These types of orbits also have the property that the perceived loiter time is different for the perigee and apogee.
At perigee (closest to Earth) it will be moving very fast and so any changes to velocity will have a large impact (easily change orbit).
While at apogee it will appear to sit in space and move quite slowly. As an example this is used for the Russian GPS system so their satellites can sit in high earth latitudes for longer needing fewer satellites to cover Russia.
You may be thinking of highly-elliptical molniya/lightning orbits (1), which enabled state TV broadcasts for high-lat places in Siberia.
It's used for communications satellites and is called the Molniya orbit[1]. Their GLONASS (positioning system) satellites use circular medium altitude orbits, but with a higher inclination (about 65 deg vs. GPS's 55 deg).
Burns at closest approach (perigee) have the largest influence on total orbital characteristics. Burns at furthest approach (apogee) can raise the entire orbit if desired.
(Or so I understand.)
Burns at apogee have best efficiency for out-of-plane maneuvers (change orbital inclination plane) due to lowest velocity of the spacecraft.
Highly elliptical orbits can do both at a few hours' notice.
Burns don't have to happen only at perigee/apogee so there's more flexibility in practice. And counter intuitive stuff like bi-elliptic transfers.
It's funny, I remember first learning to use such arcane maneuvers in a game called Children of a Dead Earth, in order to get into a terribly low orbit of Neptune to strike a methane refinery... My poor brain was always used to simple Hohmann transfers in games like KSP!
The US Space Shuttle could similarly "change payloads", with its modular payload bay capable of carrying either one-time cargoes (often satellites for launch), or reusable modules such as Spacelab, parts of which flew on a total of 35 Shuttle missions.
<https://en.wikipedia.org/wiki/Spacelab>
But modularity is also inherent in conventional rocket-based launches, with cargoes fitting within the fairing bay capable of being deployed or orbited.
Changing payloads in space is a rather different prospect, though the ability to rendezvous with, take on-board, and de-orbit satellites (man-made or artificial, the US's own, or other nations') is another possible capability. The X37's small size gives only limited potential here, and I'm pretty sure that if the US were snatching other nations' satellites we'd have heard about it.