An easement is essentially a right of way access agreement between a public or private entity and a property owner.  It is a right to cross or otherwise use someone else's land for a specified purpose.  Some examples of easement types are those for utilities, drainage, or temporary construction.  Most easements have some rules regarding the use of the land in the easement with regards to planting, building, or any in ground structures.  Your deed would recognize the existence of an easement if your property had one.  You should contact the easement owner to find out more detailed information.