Another Tor noob

Hello,

Sorry if this has come up before, but I can't find any satisfactory answer.

When I first start Tor, where does it get the list of nodes I can connect to? I believe it may be stored centrally, but I don't really understand half of the documentation. If I run a node but only when I am also using Tor as a client, how would other people know to connect to me and to stop connecting when I turn it off?

Related to this, if my ISP is malicious, could they possibly serve me a list of "nodes" which are running Tor but controlled by them? Or could they spoof the IPs of nodes that I am connecting to and spy on my browsing that way?

Thanks for any help or if you can point to a doc that explains this stuff simply.