Degrees of freedom (often abbreviated as df) refers to the number of values in a sample data set that are free to vary after certain constraints have been imposed on the data.
Think of it like this: Imagine you have a big box of different colored blocks. You want to build a tower with them. However, you can only use a specific number of blocks, and you have to follow some rules. For example, all the blocks must be the same size, and you can only use red and yellow blocks.
In statistics, your "blocks" are the data points that you have. Just like how you have rules for which blocks you can use to build your tower, different statistical tests have rules for how many data points you can use, and what characteristics those data points have.
The number of degrees of freedom tells you how many data points you have to work with after these rules and restrictions have been imposed. To continue with the block example, if you could only choose 10 blocks to build your tower, but 6 of them had to be red and 4 had to be yellow, you would have 9 degrees of freedom: you can only choose 9 blocks freely, because one of the colors is already determined.
In statistics, degrees of freedom play an important role in calculating the reliability and accuracy of statistical tests. Having more degrees of freedom generally makes your results more reliable, while having fewer degrees of freedom can introduce more uncertainty and error. It's kind of like having more blocks to build with - the more options you have, the more likely you are to build a sturdy, successful tower.