An express easement is one that is granted in a deed or a will. Express easements are the most common and must satisfy the statute of frauds. The statute of frauds dictates that certain things be in writing to be valid and enforceable. An easement by express grant must be in writing. These easements typically describe the property and name the grantor and the grantee.
An implied easement is an easement that is implied by prior use. Usually, implied easements arise when a property owner split one parcel of land into two, sold the second parcel and kept the first. Where the landowner used a driveway across both parcels, it will be implied that the owner of the second parcel also gets use of the easement, as its use preexisted the separation of the one parcel of land into two.
By Prescription and By Necessity
Easements by prescription are similar to the law of adverse possession. An easement by prescription is granted to someone who has "adversely possessed" another person's property for the statutory period, as prescribed by state law. Typically, easements by prescription arise when one neighbor uses a portion of another neighbor's land --- often, as a driveway --- continuously for the entire statutory period. An easement by necessity is often granted by courts when a landowner proves that his property is landlocked and he cannot otherwise use it without being granted an easement.
Affirmative and Negative
All easements are either affirmative or negative. Affirmative easements are the most common type; these easements grant the owner the right to do something, such as cross over a neighbor's land. A negative easement gives the easement holder the right to prevent or prohibit someone from doing something, such as blocking sunlight or a view.