What is the funny-looking "i" in the palette?

*To*: mathgroup at smc.vnet.net*Subject*: [mg6539] What is the funny-looking "i" in the palette?*From*: robpeterson at sprintmail.com*Date*: Mon, 31 Mar 1997 23:01:38 -0500 (EST)*Organization*: Sprint Internet Passport*Sender*: owner-wri-mathgroup at wolfram.com

Now that I've found the palette, I wonder what some of the symbols in it mean. Since there is vanishingly small info on the notebook interface (in 3.0), I spent quite a bit of time looking thru the help files and the book but found no clues what this funny i is (it has two vertical bars, not one plus a dot). At first, I thought it meant Root[-1] but only capital I works for that, I tried it. Any clues would be appreciated.