It's the use of Instant Message/Chat applications to talking tickling with someone, often in "virtual" tickling play. Works very well, erotically-speaking, for some, and not for others.
As you've a Yahoo email address, you could easily use Yahoo Messenger. If this is your vanilla (non-kink-related) account, you may wish to create a different account for use in such activities.
There's many cool folks around here. Private Messages are another way to reach many (PMs).