[kurumo]

Imagine I want to send a letter to someone, but I am worried that it may be intercepted (by the government, for the sake of argument). So instead of sending it directly to my recepient, I make arrangements with some reliable friends so that if they receive a letter from one of us, they take it out of the envelope and put it in different one, addressed to another friend. To make sure the letter doesn't travel forever we add dots at the end; once there are more than three (four, five...), we send the letter to the original intended recepient. Nobody knows for sure who is the person who sent the letter originally (as I can put different number of dots at the end of the letter). We can also make it so that none of the intermediate parties know what the message says (possibly even who is the final recipient?) by encoding the message at every step and using extra envelopes. At the outset I write my letter, add some dots at the end and send it to one to my friends, picked randomly, together with an extra envelope addressed to the intended recepient.

That should do as far as Tor goes, but the more general problem of explaining why is such a thing needed by your mom is much harder. (Unless she lives in North Korea or some such place).