Recent years have witnessed a lot of endeavors in spintronic field, i.e., the concept of altermagnet and its implication of combining advantages of conventional ferromagnetic and antiferromagnetic systems together. Many works have been carried out on design of new altermagnets with fanscinating feature, we aim to look at the difference between AFMs and AMs. In the seminal editorial report, AMs in general could exhibit anomalous Hall effect, while it is completely silent in AFMs. However, it has been soon realized that anomalous Hall is not a sufficient condition for AMs, as they are essentially two different sets with some overlaps. We conduct group theory analysis to suggest that one may use a light-induced spintronic strategy to distinguish them. The AFMs only show Neel vector torque, while the AMs could give observable spin canting. We carefully enumerate all the 122 magnetic point groups to list all of them. The concept is furthermore illustrated via low energy models and ab initio calculations of representative materials. One may read our recent paper in PRL, at https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.134.176902 for further details on symmetry derivation.

***Recommend: Editorial, "Scientists are workers", Nat. Rev. Phys. (2025) https://www.nature.com/articles/s42254-025-00832-6 to celebrate the International Workers' Day.