How does the bitcoind get current blocks when we start that? Bitcoind tries to save all of blocks when we start that and  I came to want to know about it more so I've been searching for that but I couldn't figure it out.
So now I just guess that bitcoind tries to save all of blocks by connecting to users' pcs 
Is my guessing right?
Yes, bitcoin downloads all its blocks off other bitcoin nodes that it connects to, hence the term peer-to-peer (P2P) network. During the initial block download, when a node starts for the first time, it must download all blocks since the beginning of bitcoin (the genesis block), so it must download these from full nodes which store them all, unlike pruned nodes which only store some of the blockchain, not the whole thing.