Networking – Problems with RD, RT-Import and RT-Export in MPLS VPN and BGP

I am learning MPLS VPN with MP-BGP and I have difficulty finding the RD value and the RT import and export values.

After what I already understood, RD (distance stopper) Identifies the VRFs from a network that makes up the same virtual network and changes the routing information between them. Import RT indicates which VRFs in a network are known to the local VRF and Export RT is sent to identify the information from the local VRF.
To decide in which VRF the router will be installed, if a package will come into the PE, if the RT export has the package and the RT import has our VRF the sameit adds the route to the VRF, otherwise it clears it.

I do not know if everything I've written is right. But I do not understand it right when I find something like that.

Let's talk about the locations PE1, PE2, PE3 and PEC (Central PE).

Which sites does PE3 know?

Is it true that PE3 knows no other network? Because when it sends information to PEC and then PEC compares the RT export of PE3 and its RT import, they do not match.

Which websites does PEC know?

I think PEC knows PE1 and PE2 because the RT export of PE1 and PE2 matches the RT import of PEC.

Am I right? Please, I need help to understand it.