[jQuery] Context querstion

Why is the context of this one the document: $('div.layer').find(':checkbox') or $('div.layer').eq(0).find (':checkbox') and at this the div.layer $($('div.layer').get(0)).find(':checkbox')

[jQuery] Remove from selection

Ho can I remove an specific element from a jquery selection. I have a selection of dd and dt of an definition list.Now I remove a specific one, using remove(), but in the selection the element is still there. I've read the manual so I know its a feature but how to remove the element without queryi