WHAT DOES SOLE OR FULL CUSTODY ENTAIL?

There are 2 types of custody: physical and legal. Sole physical custody means that the child lives with 1 parent full time. This is not unusual in your situation where both parents are living in different states. The child can't live in 2 states at the same time. Sole legal custody would mean that only 1 parent makes all the decision regarding the child, such as health decisions, school decisions, etc. Usually, both parents are granted joint legal custody unless one of the parents is unfit. If your ex is asking for sole legal custody or you oppose her having sole physical custody, you need to consult a family law attorney to represent you and make sure that your parental rights are protected.

http://family-law.freeadvice.com/child_custody/common_terms.htm

Sole legal custody and sole physical custody are two types. Sole legal is only one parent gets to make all the decisions regarding the child: health, welfare, etc.
Sole physical custody is one the child remains and live with only one parent.

Is she filing in Virginia? Are you planning on filing in California?

In California, see:

3000.  Unless the provision or context otherwise requires, the
definitions in this chapter govern the construction of this division.



3002.  "Joint custody" means joint physical custody and joint legal
custody.


3003.  "Joint legal custody" means that both parents shall share the
right and the responsibility to make the decisions relating to the
health, education, and welfare of a child.



3004.  "Joint physical custody" means that each of the parents shall
have significant periods of physical custody.  Joint physical
custody shall be shared by the parents in such a way so as to assure
a child of frequent and continuing contact with both parents, subject
to Sections 3011 and 3020.



3006.  "Sole legal custody" means that one parent shall have the
right and the responsibility to make the decisions relating to the
health, education, and welfare of a child.



3007.  "Sole physical custody" means that a child shall reside with
and be under the supervision of one parent, subject to the power of
the court to order visitation.

In Virginia:

§ 20-146.1. Definitions. "Physical custody" means the physical care and supervision of a child.