The Japanese Language Proficiency Test
The Japanese Language Proficiency Test (JLPT, 日本語能力試験) comes in four levels. Level one (1級) is the hardest and level four (4級) is the easiest.
The JLPT is only offered once a year in December in select locations, and it may involve some traveling for you to take the test. It is also a bit expensive.
Because the third and fourth levels are very easy, I recommend skipping them. The JLPT usually involves too much travel and is too expensive to be worth preparing for the 3-4 levels. Also, because they are so easy, no one will care that you passed them. Instead, just spend more time studying and prepare for the 2kyuu and 1kyuu.
What kind of test is the JLPT?
The JLPT requires you to not just get "the gist" of things, but rather understand deeply subtle grammatical points and have comprehensive knowledge of kanji.
While it is called a language ability test, the entire test is taken in a multiple choice (four answers possible) format. So, there is no speaking or writing required, but that doesn't mean it is easy.
Instead, the JLPT, particularly at its hardest level, focuses on somewhat obscure grammar with which many native speakers encounter serious difficultly. For this reason, a significant amount of preparation for the JLPT will be preparing for the test, and not studying the Japanese language in particular.
Still, it's not all bad. It can be a fun test to take (at least if you're like me), and the difficultly level is high, so you will actually feel accomplished when you pass it.