A basic hypergeometric series is like a math toy box with a special formula that helps you put together certain patterns of toys. You start with a certain type of toy, called the base toy, and then you keep adding more and more toys that are related to the base toy in a special way.
Now, the cool thing about this formula is that it tells you how to add up all the toys in the pattern, even if there are infinite toys in the pattern. You just plug in the right numbers into the formula and out pops the sum of all the toys in your pattern!
For example, let's say you have a pattern of blocks. You start with one yellow block as your base toy. Then, for each new block you add to the pattern, it has to be either green or red, but the number of green blocks always has to be one more than the number of red blocks. So you might have a pattern that looks like:
yellow, green, red, green, red, green, red, ...
This is a basic hypergeometric series because each block is related to the base toy in a very specific way. And using the special formula, you can find the sum of all the blocks in the pattern, even if there are an infinite number of blocks!
Of course, in real life, we don't usually play with blocks like this. But this formula is really handy in lots of different kinds of math and science problems, like calculating probabilities or finding patterns in large sets of data. So it's a pretty cool toy box to have in your math toolbox!