Applying for US wife

[digitalrev]

Dear members.
I am planning to apply for my wife. But I am a bit confused with the whole process. Can someone please shed some light.

I am married to a US citizen for last 5 years, My annual salary is above 20K which meets the financial requirements set by the home office. My questions are :

1. I know I would need to send all the relevant documents to Shefield office, but for application to process does my wife need to send her passport to homeoffice branch in the UK or UK embassy in the US? How does she get a visa? is it some sort of stamp or biometric card sent by post?

2. She often visits UK under the visa weaver program, is she allowed to visit UK while her application is being proceeded?

Thank you