Can a node exit the bitcoin network and return to his address and transactions? I have read in Wikipedia that "Messages are broadcast on a best effort basis, and nodes can leave and rejoin the network at will " in bitcoin network. what does it mean that a node can leave the network-what will happend to its transactions? Can he get back to the same address and claim his transactions again (its bitcoin)?

thank you
Transactions are not directly sent to the node that holds the private keys for the addresses involving it. Rather transactions are broadcast to all nodes on the network and then recorded on the blockchain. When a node rejoins the network, it downloads and verifies the blockchain from its peers. When it does that, it scans the blockchain for transactions that pertain to it.

The process of receiving is completely passive; there is no direct sending to the receiver (the sender does not have that information) nor is there a claiming process.