No such things as silly questions.
Newer versions of Teamviewer can be set to wake machines that are sleeping
A laptop with a closed lid is probably NOT going to allow this. TV would require the laptop lid to be open (i think)
If you have a teamviewer icon in the system tray, then yes someone can access your computer.
Hopefully you have set a hard permanent password, and set a new random password every start, or disabled random passwords
Teamviewer can be set for unattended access, so that other end can connect at anytime, even if no-one is there. ( I do this for all machines that I manage as an IT tech)
You can also set your temviewer to not allow that, or to ask permission everytime...(I do this on MY computers)
conversely, It can also be set to show a blank screen and disallow local keyboard and mouse input. ( i do this for machines that I manage, where I know they are in a public area, and I am likely to access confidential material on that machine)
If you are using your computer, then you will notice someone taking it over with teamviewer (unless you use remote desktop on a server operating system, and they take over the 'console' session).
If in doubt, turn off Teamviewer and set it not to start when the computer is turned on, and only start it when you need it...