I am a little confused about the purpose of a spousal IRA.

If I am the only wage earner in the family, do I have to open a spousal IRA for my wife in order to put money into it?

Can she open an IRA while she is still working and continue to put money into that account when she is no longer receiving earned income?

I believe that we can contribute $2000/year for her, regardless of employment status, but how do the mechanics of this work out?