A fun part of living thousands of miles from family and friends is sending packages home — that is, so long as you know the requisite jargon to communicate at the yūbin kyoku (郵便局, post office).
Nihon Yusei Kousha (日本郵政公社, Japan Post) became mineika (民営化, privatized) in 2007 and is now called Nihon Yusei Kabushiki-gaisha (日本郵政株式会社, Japan Post Holdings Co., Ltd.). It offers three main areas of service: yūbin (郵便, mail), chokin (貯金, savings) and hoken (保険, insurance).
Yūbin includes sending kokunai haisou (国内配送, domestic mail) and kaigai haisou (海外配送, overseas mail). For that package you plan to send your folks, you have the options of kōkūbin (航空便, airmail), funabin (船便, sea mail) or EMS, which is an express service. Take your kozutsumi (小包, parcel) to the madoguchi (窓口, counter) and say, "Kōkūbin de onegaishimasu"(「航空便でお願いします」, "By airmail please"), or substitute funabin or EMS for kōkūbin.