Answer:
A lawsuit is when someone sues you in court. There are two kinds of lawsuits. One is criminal and the prosecutor brings that lawsuit and it is because you are being charged with breaking the law - commiting a crime. If you are stealing or stealing services, that could be a crime and result in the prosecutor charging you with a crime and that is a lawsuit.
The other lawsuit is civil suit. That is when someone sues you for money - for damages or to enforce a contract.
For instance, OJ Simpson won a lawsuit when he was sued for murdering his wife and the waiter. (Proof of guilty is beyond a reasonable doubt). However, he lost a lawsuit to the parents of Nicole, his wife, in civil court and it was for damages - money for loss of their daughter's life. That is a different kind or level of evidence required and that is guilt with a preponderence of evidence. Preponderance is like 51% while beyond a reasonable doubt is very much higher level of proof involved.
But both these are lawsuits. Having a lawsuit filed against you doesn' mean you will be found guilty or lose the suit. Anyone can bring a suit and many are on flimsy reasons. There is, in some courts, if not all, a penalty against an attorney who brings a frivolous lawsuit. However, I don't know how often the courts would find that it was frivolous. Would have to be so reidiculous that no one would be likely to think they have a chance. however, if there is a question as to whether or not there is a good lawsuit, or any suit that could possibly win, then it isn't frivolous.
Now this is not a legal opinion as I am not a registered attorney so this is just personal information from a rhetorical position or personal opinion, not a legal opinion.