Using the same apps on iPhone AND iPad.

If I have Facebook & Twitter on my iPhone 4 AND also on an iPad - can someone clarify what would exactly happen?!

Example - I open Twitter on my iPhone on Saturday and read all the current most up to date tweets.

Then, on Sunday, I open up Twitter on my iPad - does it know that Saturdays tweets have already been read(on the iPhone) so only shows tweets from that point on OR, will it still show Saturdays tweets as well?!

Essentially, I think I'm basically asking this - if I'm running 2 identical apps (1 on iPhone & 1 on iPad) do they kinda work in conjunction with each other or are they 2 totally independent apps?! Does that make sense?!

I know what I'm trying to say but difficult to describe!!!

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