An EAD, which stands for Employment Authorization Document, allows the holder to work in the U.S. Certain H4 visa holders are eligible to apply for an EAD when the primary H1 visa holder’s Form I-140 (immigrant petition) is approved or H1 visa holder extends beyond 6 years under AC21 rule.
Unlike an H1 visa holder, who can work only for the sponsoring employer, H4 EAD holders can work anywhere during the validity period of the H4 EAD.
You will see that the category given to H4 EADs is “C26”.