Trackmaster consists of motorized trains and push along trains. Push Along trains are not motorized, hence the name "Push Along."
Push Along for the Thomas & Friends Trackmaster system is a new product line for 2019 that replaces Thomas & Friends Adventures. Trains in the Push Along product line are metal with some plastic parts and have been re-designed with wider chassis (to fit on Trackmaster track) and different couplings (to be able to attach to the motorized Trackmaster trains). Trackmaster Push Along trains are not motorized and are not compatible with Thomas & Friends Adventures.