If you want to know what your network topology is, then the first thing you need to do is understand the different types.
I suggest you either use the world wide web and a search engine such as Google or a book to find out the difference between a star, a bus etc. and then you should be able to easily identify your own type. I would recommend finding an image of the topologies as you'll probably find it easier to understand.
In short however, if your running just a basic home network then the chances are it shall be Physical, and a Star network. The reason being that you're running actual hardware as opposed to using software to create a virtual LAN (vLAN), and the star are your devices revolving around your router/modem.
I don't know why you need to know this, but if it's for network engineering/administration then STOP. Don't touch a network if you don't know anything about network hehe
If it's for training then I'd recommend the foundation certification CompTIA Network+
If it's for a one off thing and you have nothing to do with networks, then Google is your friend, my friend.
Now - if you have a network or are on a network I'd imagine you have an outsourced IT service provider or an internal IT team; ask them. They'll probably ask you to vanish and might even beg you to never return but at least you'll know!
I'd be amazed if all of your answers weren't on this wikipedia page that is dedicated to network topologies.
As for infrastructure you need to add clarification. What are you looking to find out? How many physical hosts you have as well as how many virtual hosts you have? What technology you are using for virtualisation? Your physical and virtual specifications? If so - then the chances are you're not authorised to know.
plz how can i know whats my network architecture type (physical or logical)? and what topology used in it (star,bus,ring)?!!
A network will have both a physical and logical implementation. The physical deals with the actual physical layout of the network (cables, equipment, etc..), while the logical deals with the network flow of data on the network.
For example on a shared ethernet network (hubs and ethernet cable) the physical topology is star because each node connects back to a central device (hub), but the logical topology is bus because in shared ethernet, all of the devides share the same media and can communicate at any given time not dependant on a token or other mechanism for communication.