Suppose you buy an Internet plan for $50. On your bill, it'll be $50, plus usually 5-10 other fees probably totaling around $5-10. Some examples from my cell phone bill are

• Fed universal service charge
• regulatory charge
• admin & telco regulatory charge
• gross receipts surcharge
• state public safety comm surcharge
• local public safety comm surcharge
• state sales tax

That's 7 additional fees, whose names vary from somewhat comprehensible to uselessly vague. And you won't find these prices until you get your bill. They're not advertised directly, instead you'll see that $50 advertised price, and a little asterisk that points to tiny text "additional fees may apply" that somehow make this all legal.

The FCC is saying if telcoms are going to add all these fees, they need to be part of the ad and not hidden.

This is about "fees" over and above the advertised "price". So it says your plan is $65/month, but when you get your bill it's actually $95 because there's a "Cost Recovery Fee", a "Network Maintenance Fee", and a "Municipal Area Surcharge" (IIRC all real fees I've paid on an internet bill) on top of the advertised rate. They're often meant to look like taxes, but they aren't.