Short Term Missions (STM) Is a valuable ingredient in any individuals or church's missions repertoire. Though it is overhyped and often done poorly, It can be a fascinating insight into missions ministry and missionaries you serve, and your own personal calling.
Short-term missions refers to field ministry visits, usually with a very specific purpose or event in mind, lasting anywhere from three days to a full year. Often, and STM deploys as a team of 3 to 30 people. We like to see STM teams have a spiritual component and not simply some material building project. Also, the STM team usually is involved in doing something requiring a lot of manpower that can't normally be done by the missionary on the field by themselves.
There is a lot of literature, training, and Internet available information for every aspect of STM ministry.
If you are considering whether or not God may be calling you to be a missionary, and STM experience is an invaluable ingredient to test your heart and mind and body with an actual short term experience that will teach you a lot about missions and about yourself.