A more thorough explanation:

Strikers are employees who stop working in order to protest or demand something from their employer. There are two types of strikers:

Economic strikers are employees who stop working to ask for better pay, shorter hours, or better working conditions. They are still considered employees, but the employer can replace them with new workers. If the employer hires new workers, the economic strikers can't automatically get their old jobs back. However, if the strikers haven't found new jobs, they can be called back to work when there are openings. The strikers or their representatives must ask for their jobs back.

Unfair labor practice strikers are employees who stop working to protest against something their employer is doing that is against the law. The employer can't replace them with new workers. When the strike is over, the unfair labor practice strikers can go back to their old jobs, even if the employer hired new workers to replace them.

For example, if a group of workers at a factory stop working to ask for better pay, they are economic strikers. If the factory hires new workers to replace them, the economic strikers can't automatically get their old jobs back. However, if the strikers haven't found new jobs, they can be called back to work when there are openings.

Another example is if a group of workers at a restaurant stop working to protest against their employer not following the law, they are unfair labor practice strikers. The employer can't replace them with new workers. When the strike is over, the unfair labor practice strikers can go back to their old jobs, even if the employer hired new workers to replace them.