Allow me to explain:
When you sign into a Teamwork project, you sign out a bunch of stories, layers, elevations, and details, collectively called a workspace.
While you are working, you can save that "workspace" anywhere you want, to a network, to a laptop, or to a desktop's local hard drive. When you save, you are saving a PLC file (also called a local draft). If you save the PLC, then stick it on a thumb drive, you can take it home with you.
The PLC has all of the elements that you signed out Read/Write. It also keeps the rest of the project Read/Only, so you can see whatever you want but cannot edit it unless you claimed it at the Sign In menu.
The key is that if you quit Archicad and turn off your computer, your PLC is still "active". Those elements still belong to you. No one else can edit them until you use the Teamwork > Sign Out or the Change my Workspace command to release them.
When you get the PLC home, you use the Archicad File > Open command. Work on it all you want, and save it like you would if it were a PLN.
When you bring it back the next day, you will File > Open the PLC file in Archicad and click Teamwork > Send & Recieve. That pushes all your changes back to the main PLP file and pulls any changes that someone else made to elements that you did not have signed out.
The moral of the story is that "Send & Receive" saves all your work back to the PLP file. Anything else, only you can see.
The idea of making alternates is that you Sign In, then immediately save a PLC, probably named "basic" or some other name. From there, you save your first option as "option1.PLC", your second as "option2.PLC" and so on. At some point when you pick which option is going forward, you open that PLC and click "Send & Receive." That work is saved back to the PLP. Now after you do that, NONE of your "optionX.PLC" files are valid anymore. You can keep them around and look at them if you want, but you will not be able to Send/Receive from them anymore.
Does all that make sense?
Tom Waltz