I believe they're just as follows:
make just refers to creating an instance of the struct and setting its values:
FMyStruct MyInstance = FMyStruct::Make(42, "Hello");
while break is for extracting values
int32 ExtractedValueA;
FString ExtractedValueB;
MyInstance.Break(ExtractedValueA, ExtractedValueB);
I believe the terms are common in blueprints too.