What are the specs on the genset?
Generator basics:
A single phase generator typically has 2 hot leads and a neutral/ground. Each hot leg(or phase) measured to neutral is 120VAC. One hot leg measured to the other is 240V. This is the same as what is run into the typical american household(2 hots, neutral and ground) and what most household power panels are built to distribute. A 10KW single phase generator as I just described can only deliver 5KW out of each 120V-Neutral connection. the distribution panel, like that used for the commercial power feeding your home must have the loads wired to the circuit breakers so that the two available legs are balanced to get full power out of the generator without overloading a single leg. 240V loads will draw their current equally from both legs so they are not a problem.
A 3 phase generator is similar to what I have described above except there is an additional hot lead/leg. Any of the 3 hot legs measured to neutral will be 120VAC, any hot measured to any other hot will be 240VAC. 3 phase power is typically used in industrial applications, particularly those that employ large horsepower electric motors. It will require a 3 phase distribution panel to get the full capacity out of the generator. You could wire 2 of the phases into a standard domestic panel, but the generators rated capacity is divided amongst the 3 phases. IE, a 15KW 3 phase generator can only support 5KW on each of it's 3 legs, or 10KW to a 240V load applied across 2 of the three legs. Because of this, a 3 phase generator needs to be a third larger than it's single phase counterpart to feed a typical domestic load. That means larger engine and greater fuel consumption for a given application. If the generator is Diesel powered, you may never be able to operate it near it's optimum loading using only 2 of the 3 phases. An underloaded diesel can have longer term mechanical problems and requires more frequent oil changes to deal with fuel oil diluting the lube oil.