Yep! Four twisted pairs. Each can carry a phone line. Tip and ring!

I think you meant RJ11. Ethernet uses RJ45.

But that’s just the jack. Either can use CAT5/6/7 cabling and most RJ11 in more recent homes is still CAT5 or better. But that doesn’t mean the builders didn’t staple it to the studs making it worthless for anything more than 10BASE-T (if even that).