Quick Understanding of software product requirements and technologies around them are important qualities expected from any engineer. However, I believe
it is THE most important and must-have skill for a QA engineer. Why is that?
In theory, a QA cycle is supposed to start with test analysis and design. Requirements specifications/design specs are the ultimate references to derive test scenarios and
test cases in test analysis/design phase. But those reference materials are not always available in early stages of the development and in some projects you don't even see such docs.
Even if you have the documented requirements and design docs, you don't get the feel of actual business flow and scenarios until you play around with the
working instance of the product. There were thousands of test cases written by referring to functional specs, however the real business
scenarios may have missed due to the lack of understanding of the domain and nature of the product.
When the initial builds are released for QA testing, you will get a better knowledge of the product and its domain while you play around the features of product.
You will start to realize the functional flows documented in test scenarios (which were derived using requirement specs) and sudden requirements to aware of new technologies will arise.
However you don't get much time to learn every bits of business domain and related technologies with the frequent test build releases.
This is where your quick learning ability comes in to play. If QA engineer possesses;
-grasp things with minimum time
-eager to find out how it works
-Love to read
then I always believe such QA engineer is capable to move forward in a challenging environment.
Remember, QA is expected to act as user's advocates and should know what and how the product functions. Therefore catching the things as quickly as possible
and apply them in testing are key to deliver a successful QA outcome.