Cervical lordosis is a curve in the cervical spine, the area of the spine which contains the neck vertebrae. This curve is entirely normal and in fact desirable because it helps to stabilize the head and spine, but when the curve straightens out, becomes too deep, or faces in the wrong direction, it can become a problem.
If something's canonical, it follows a principle or rule, usually in a religious or church-related situation. It is also used in mathematics, music and can refer to something reduced to its most basic form.
In this case, in a client/server context, the canonicalization would be the responsibility of the client. In summary, a standard form of representation for data. From this form you can then convert to any representation you may need.