The nursing licensure compact is one of the most convenient things to come around for the travel nurse in a long time. Some love it, some don't, either way it does make traveling much easier.
Before the implementation of the compact license, you would need a new nursing license for every assignment that you took in a new state. The travel nurse companies recruiters would assist you with obtaining the licenses you needed. (They still do a great job with this for the non nurse compact states and are an incredible resource for questions.)
If you are a resident of a state that participates in the nursing compact license, and hold their compact license, you can travel to other participating compact nursing states and work on your home license.
You won't be required to get that states license.
This is wonderful for a number of reasons.
Not all states participate. You will need to see the NCSBN website for all the participating states. They keep it updated regularly which is important since new states are being added yearly. Be careful with any other list you find as it may not actually be correct.
If you are going to do travel nursing, definitely consider the compact nursing license as an easy way to keep you mobile.