I've started using Bitcoin few days ago. I've made few transactions, but I am not sure about whether my IP address is really hidden. Are IP addresses recorded in transaction logs?
Can somebody track my transaction and find my IP address (eg. recepient of the payment or somebody who know my bitcoin address)?
They can find all the IP addresses connected to the BitCoin network. But the client 'trickles' out its own transactions. So if you send the transaction to A, B might get the transaction from A long before you send it to B. So how does B know whether you created the transaction or A did?
I see Proxy options in Bitcoin client setting. Why would there be an option to set a proxy if there is no way to track my IP?
If your computer is behind NAT but has access to a proxy with a public IP address, connecting through the proxy would allow it to accept inbound connections. Some computers only have Internet access through a proxy because they're behind firewalls that deny all traffic they don't understand, and they don't understand Bitcoin.