Boundary lines help determine the extent of a property and its legal ownership. Specifically, these lines define a property's physical limits and help prevent conflicts between neighboring property owners.
You and your neighbour can create a 'boundary agreement' to record: the boundary between 2 properties. who's responsible for maintaining a hedge, wall, tree or fence between 2 properties.
The boundary line is where the property ends. An easement is aright to cross over your property. Most easements are for utilities or access to a property. Both are pretty much written in stone and beyond your ability to control.
California law recognizes the right of two adjoining landowners to agree on a specific line or marker to act as the property lines between the two parcels, notwithstanding the legal description in each parcel's deed.
Under such an agreement, the parties acknowledge the true boundary line between the properties, and the encroaching owner releases any claim to the strip of land encroached upon. In return, the “encroached upon” owner allows the encroachment to continue for so long as he/she is not adversely affected.