Some networks ban any kind of Tor traffic through their systems by blacklisting all known entry nodes. To get around this ban, you can connect to a bridge. A bridge functions similarly to an entry node, except that you have to obtain IP addresses manually. Using a bridge to connect to the Tor network does not have any significant drawbacks, but in many situations will not be able to circumvent Tor obstructions. For better results, first connect to your VPN, then to the Tor network.
When you are connected with a VPN, neither the sites you are visiting nor the Tor entry nodes will know your true location, though the VPN company will. However, the VPN company cannot see the content of your traffic, even if they tried to, as the traffic is encrypted between you and the Tor entry node.
Theoretically, there is also the option of connecting first to the Tor network, then tunneling a VPN through it. This makes it impossible for your VPN provider to know where you are, and ensures exit nodes can’t read or alter your traffic. This helps little with anonymity, however, which is why most VPN providers do not support this function.
Depending on whether you use Tor, VPN, or a combination of the two, sites and networks can see different information about you.