What does a "cash offer" really mean?

[Account Closed]

I feel silly even having to ask this question, but how exactly does a "cash offer" transaction occur on a home/lot?  Deals are moving quick in my area, often with several cash offers made in the first day a deal is available.  

Are most of these folks just making offers with no financing contingency, then tapping lines of credit or using other instruments to close these deals, or are they literally wiring cash from their checking accounts at closing? One builder I spoke to said he always offers "cash", but usually that just means his bank will give him a proof of funds letter and then he figures out how to close it after that.  

In the large multifamily world in which I work, most everything is bought with financing and even when someone says they are offering cash, it is still financed somehow.  We never include a financing contingency, but the assumption is always that the deal will be financed.

I'm sure there is a simple explanation for this that I'm missing.