The command Findall, often abbreviated to fa, gives you a list of the people who are currently on the muck. It also gives a certain amount of information about them, including: the last time they did anything (how long they've been idle), how long they have been on in total, their location, and whether they are IC or OOC.

To use it, simply type fa. If you type fa <name> where <name> is the name of the person you want information about, it will give you a list as above, but with only that person's name on it.