Spooky-Mono (who I mentioned above) is the boyfriend of RedPepper and they live together with her husband Polynerdist.
So, you might read through her blog too.
As for secondary-I think it really comes down to individual opinion.
My husband would classify my boyfriend as being secondary. But, I can't say precisely why.
I have always classified them both as primaries.
Mono once explained it in terms of joint responsibilities. He considers himself secondary-because he's not the husband, he doesn't share the parenting role of the child and he's not co-owner of the property. (I'm not quoting-I'm too lazy to search for the exact post).
Others have defined it by how much time they spend together.
Others yet have defined it by how they feel for the people.
SOOOOOO, since you are a newbie-then you can pick your own definition if you choose to use the term.