Each kind of initiative follows its own path through Congress. Pick one to see its steps, explained one by one.
A decree with force of law issued by the Government under urgency. Congress must ratify or repeal it within 30 days.
Binding: if it passes, the law changes.
The Government passes it as an emergency measure and it has the force of law from its publication in the BOE, before Congress votes on it.
A member of the Government defends it in the plenary and the groups state their position. No amendments are allowed.
Within 30 days of its publication, Congress votes to validate it (it stays) or repeal it (it lapses). If validated, Congress can also choose to process it as a bill so it can be amended.