ppp and VPN

I am researching using VPN in windows 2000 server. That is PPP and PPTP

You are at home, and you dial into and ISP to make a VPN connection to you company’s LAN.

Does the PPP connection end at the ISP or does the PPP connection go all the way to your company’s LAN

Or does the PPP connection end at the ISP, and then PPTP extends the connection from ISP to your
company’s LAN. Which way does it work?