The two-person form practiced by some branches of Yang Style is usually called Sanshou ("sparring"? in Chinese), but that term also refers to a sport-form of martial arts popular in China. The form I have seen can be viewed here
and has 88 postures with an A and B side.
My understanding is that this form was invented by certain students of Yang Chengfu, but is not taught by the Yang family itself.
As Michael, touched on, the family teaches various circling patterns that typically include two to four energy techniques in a repeating sequence. There are ways to transition between patterns, combine them with various stepping patterns, and use variations to move pretty much however you want without disrupting the flow with your partner. After you have some mastery of the patterns, you can practice applications of the energies, applications from the bare-hand form, counters, and counters to the counters, etc. You can also just circle and/or step in free-form spontaneous manner.