JLPT which stands for “Japanese Language Proficiency Test” is a test to measure abilities of Japanese for people whose are not native speakers of Japanese. JLPT can be taken not only in Japan but also in some cities all over the world. JLPT is held twice a year, but it might be held only once a year in some cities. The result of JLPT can be used for immigration process, education, and national exams for medical practitioners or assistant nurses in Japan and so on.
The number of JLPT examinee is about 600,000 all over the world and it can be said that JLPT is the largest test of all test of the Japanese language. More than 60% of examinees are students and about 30% are workers. From the view of purposes of taking JLPT, one-third of examinees take this exam to measure their own ability and one-quarter take it for employment, salaries, and promotion in their own countries. 20% take this exam for employment, education and so on in Japan.
JLPT measures abilities of language knowledge including vocabulary and grammar, reading and listening. Abilities of speaking and writing aren't subject of JLPT. Thus if you want to measure your ability of speaking or writing, you may need to take other tests.
JAPAN FOUNDATION 2016, Japanese Language Proficiency Test, viewed 8 December 2016, <http://www.jlpt.jp/index.html>