To lift something is to pick it up, or raise it in the air. You'll need to lift a flag before you start waving it.
You can lift things literally, like when you lift your cat in the air to save it from your dog's slobbery tongue, or lift your glass for a New Year's Eve toast. You can also lift things figuratively, like when someone lifts your spirits, cheering you up, or when winning first prize in a contest lifts a writer from obscurity, elevating her position in the literary world. In Britain, lift is also another word for "elevator."