As with many AC power distribution configurations, you may see the same configurations referred to in a number of different ways.
In this case, Single Phase 120/240 (also seen as Split Phase, Split-Phase 240/120V), is a common household configuration seen in North America.
A single phase 120V system would typically have 2 wires - a power wire and a neutral (as well as a ground in most cases) and delivers 120V. In many cases, household appliances like clothes dryers, air conditioners, etc. may require more than 120V. In order to provide both options in a household, a split phase or single phase 120/240 setup provides 3 wires instead - 2 power wires and a neutral. The 2 power wires result from a center-tapped secondary winding that then allow for 240V phase to phase (line to line) or 120V phase (line) to neutral. (basic diagram below)
At a high level, this configuration allows for providing 120V or 240V in a single household using a single phase system.
Samsara's PM20/PM10 can be used for monitoring Single Phase Power and supports the Split Phase configuration outlined above.
Please see the PM Installation Guide for more details: https://www.samsara.com/pdf/docs/pm-install-guide.pdf