Located at the top of the window, this option specifies whether items in the suggestion list should match the case of whatever you are typing. For example, if I wanted to type in an exception expression for the KeyboardInterrupt exception in Python and the Match case option is enabled, I would have to type a capital letter K for the correct class name to be included in the suggestion list. Next to the Match case checkbox, you can also choose only the first letter's case should be matched or whether this should apply to all the letters.

I personally always disable this checkbox so that I only have to type in, for example, a lower-case k to take advantage of code completion. However, like everything we have seen in code completion (and for that matter, like everything in programming), there is a trade-off to this practice. Specifically, if Match case is disabled, sometimes the suggestion list might be populated by many more irrelevant options, which would make finding the correct API more difficult. In this case, you would have to continue typing so that the suggestion list is narrowed down.