Did a cat walk across your keyboard?
Windows doesn't have an alignment grid feature but some monitors do - especially ASUS monitors. They call it the QuickFit function.
You need to find the user manual for your monitor and see how to enable/disable the feature and if you can't find it tell us the make and model of your monitor and we might help you look for one.
Here is another topic in the community that has some examples you can read through:
Here is a screenshot from one ASUS manual: