Retaliation
Spoke up, then paid for it?
Reporting a problem at work is protected. So is backing up a coworker who did.
When the punishment follows, hours cut, a worse shift, a write-up out of nowhere, a demotion or a firing, that's retaliation. It's often the strongest claim in a case, because the timing is hard to explain away.
You don't have to have been right about the original problem. You have to have raised it honestly.
What retaliation tends to look like
Hours cut after a pay complaint
Moved to nights after reporting harassment
A first bad review in years
Left off the schedule
Fired days after a safety report
Threats about calling immigration

Protected
Things you're allowed to speak up about
These are examples, not the whole list.
Your pay
Asking about overtime, missing wages or what coworkers earn.
Safety
Reporting a hazard to a manager or to a safety agency.
Harassment
Reporting it about yourself or someone else, inside or outside the company.
Discrimination
Complaining about unequal treatment, or filing a charge with an agency.
Leave
Asking for medical or family leave, or for an accommodation.
An investigation
Telling the truth as a witness in someone else's complaint.
Questions after speaking up
I only complained out loud, not in writing. Does it count?
It can. A spoken complaint is still a complaint. Write down when you made it, to whom, and who else was there, today while you remember.
Should I keep working there?
If you can, staying usually keeps your options open and your income coming in. We'll help you decide, and tell you what to keep a record of in the meantime.