Generally speaking, this means disciplinary action (e.g., time off without pay) and accompanying documentation. While that may not sound that bad, there are a few things that add teeth:
1. Cops make OK money compared to an average citizen, but not GREAT money. Their retirement is often tied to employment with a particular city, county, etc. Too many disciplinary actions, or one really big one, will result in being fired, meaning you've also lost your retirement investment.
2. If you want a better/higher-paying job within the department (detective, SWAT, aviation, etc.), you have to get internally hired for it. If your record is tainted by documented misconduct, you're probably never going to get promoted.
3. The law enforcement community is small and paperwork follows you everywhere. Getting fired or being un-promotable will probably be known to other departments if you try to get a job somewhere else. This is why e.g., Darren Wilson had to change careers even though a grand jury cleared him of criminal wrongdoing [1].
References:
1. http://www.usatoday.com/story/news/nation/2015/08/04/darren-...