Okay kiddo, so you know how sometimes people have problems and they want someone else to help them fix it? Well, if someone goes to court to try and get help with their problem, that person is called the "claimant".
Now, when the claimant goes to court, there are some things they need to do to tell the judge what their problem is and what they want to happen. These things they do are called "acts of the claimant".
Some of the acts of the claimant might include filling out a bunch of papers to explain their problem, talking to a lawyer to get advice, or maybe even talking to witnesses who know something about what happened. All of these things help the judge understand what the problem is and make a good decision about how to fix it.
So basically, when someone goes to court to try and get help with a problem, the things they do to explain their problem are called "acts of the claimant". And those acts help the judge make a good decision about what to do.