It's the proximity sensor on a tablet which is used to work with an auto sleep/wake function. Some Samsung Tab models have a proximity sensor built into them but, somewhat oddly, that feature seems to have been removed from more recent models. (The proximity sensor on your model is what looks like a tiny hole for an extra camera lens, close to the actual camera lens).
The specs for the Huawei T5 Mediapad show that it's got a proximity sensor and a quick search on Amazon shows that there are cases available which can make use of it. e.g.
Amazon.com User Recommendation