Okay kiddo, imagine you're going on a really special trip with your parents. The trip is to a place that is very important and meaningful to people who practice a particular religion. This place is called a tirtha.
Now, imagine this special place is like a big playground with many different parts that you can explore. Each part of the playground is like a different kshetra.
So, a tirtha is a special place that people go to visit because it is important to their religion, and a kshetra is a specific part of that place that has its own significance and meaning. Just like a playground has different parts to explore, a tirtha has different kshetras to discover.