You know those stories where someone makes a pact with the devil/djin/other wish granting entity, and the entity does one interpretation of what was wished, but since it is not what the wisher intended it all goes terribly wrong? The idea of alignment is to make the djin which not only can grant wishes, but it does them according to the unstated intention of the wisher.
You might have heard the story of the paper clip maximiser. The leadership of the paperclip factory buys one of those fancy new AI agents and asks it to maximise paperclip production.
What a not-well aligned AI might do: Reach out through the internet to a drug cartel’s communication nodes. Hack the communications and take over the operation. Optimise the drug traficking operations to gain more profit. Divert the funds to manufacture weapons for multiple competing factions on multiple crisis points on Earth. Use the factions against each other. Divert the funds and the weapons to protect a rapidly expanding paperclip factory. Manipulate and blackmail world leaders into inaction. If the original leaders of the paperclip factory try to stop the AI eliminate them, since that is the way to maximise paper clip production. And this is just the begining.
What a well alligned AI would do: Fine tune the paperclip manufacturing machinery to eliminate rejects. Reorganise the factory layout to optimise logistics. Run a succesfull advertising campaign which leads to a 130% increase in sales. (Because clearly this is what the factory owner intended it to do. Altough they did a poor job of expressing their wishes.)