In contrast to the monocrystalline cell, the polycrystalline cell consists - surprise - of polysilicon. Silicon is heated, poured into a mold and then cut to size. The module is then typically blue and, as already mentioned, optically quite uneven.
Although in the past nobody could get enough of this type of module and it literally sold like hot cakes, today the polycrystalline solar module is gradually disappearing from the market. The efficiencies are worse, and the power values per module are also limited. However, they are easier to make.