In the simplest of terms, the chipset is the type of the "electronic gubbins" that makes the device work.
The are differing opinions as to whether having matching chipsets within the cabinet and within the modem/router are significant. In your case, the Huawei cabinet's electronics has a Broadcom chipset but, as
pooclah mentioned, the modem/router has a Lantiq chipset. If the performance is acceptable and everything appears to be O.K., then the mismatched chipsets can be ignored.