Chelsea have made a habit of hoarding as much young talent as possible over the past few seasons, buying young players before allowing them to develop elsewhere on loan. If The Express is to be believed (and that's a whole different can of worms), the club has shown interest in adding young center back John Stones to it's treasure trove of youngsters.
The report claims that Tottenham are targeting the Everton man, but that both Arsenal and Chelsea have also shown some interest in bringing Stones to London. The report doesn't claim that Chelsea have actually bid on the player.
Personally, I'd just as soon pass on Stones and focus our attention elsewhere. Young, English player tend to be to least cost-effective investments in modern football, and while Stones is a decent young player, the fact that he's both English and under contract for a considerable amount of time probably mean that he's unlikely to come cheap. He's also probably not an upgrade to any of Kurt Zouma, Tomas Kalas, or Kenneth Omeruo, so he's certainly not filling a major need.