A "beater bar" refers to a rotating brush that is commonly found in vacuum cleaners. It helps to agitate and loosen dirt and debris from carpets and other surfaces, making it easier for the vacuum to pick them up. Full definition
The electric power head means that in addition to the suction of the canister, there is a motor - driven beater bar brush that agitates carpet and pulls hair up into the vacuum. (petbusiness.com)
Avoid using vacuums with plastic or rubber grippers or beater bars as those can cause damage. (quickstepstyle.com)