The easement entitles its holder to some limited use or enjoyment of another's land. The easement is automatically transferred with the benefited land. The burdened land will also be subject to the easement, so long as the subsequent buyer had some form of notice of the easement. The license is a freely-revocable mere privilege to enter another's land for some delineated purpose. For example, the newspaper carrier, landscaper, and theater ticket holder typically have licenses.
Licenses are far more informal than easements.
They do not have to be in writing to be enforceable. However, they may be revoked at any time at the will of the licensor unless the holder of the license has invested considerable sums of money or labor in reasonable reliance on the expectation that the license would not be revoked. Other sorts of servitudes include the covenant and the equitable servitude. The covenant is a contractual promise made regarding land. For example, one neighbor promises another that they will not build for commercial purposes on their parcel.