Lift holds an airplane up. Lift acts in opposition to the weight of an airplane, which acts downward. Weight is the force generated by gravity. Weight always acts downward toward the Earth. For an airplane to fly, lift must equal weight.
Weight holds an airplane down.
Thrust is the forward force that is produced by the pull of a propeller or the push jet exhaust. A propeller is a small rotating wing that is lifting forward. A jet engine forces exhaust gases out the back of the engine. These exhaust gases push the engine and thus, the airplane forward. Thrust makes an airplane go.