Vim – Refresh Changed Content of File Opened in vi(m)

In addition to uprego's answer, you can press Ctrl+G (in normal mode) to get the current buffer's name as well as the total number of lines in it and your current position within it.

Update

As per rxdazn's comment, you can press 1 before Ctrl+G to get the full file path. If you press 2, you get the full file path and the buffer number you currently have open (useful when you have opened multiple files with vim).

The excellent surround.vim makes this simple — with the cursor anywhere within the tag you want to change, in normal mode, type cst<div> (change surrounding tag to <div>). The tag name will be changed to "div" in both the opening and closing tag, and you'll be back in normal mode.