Tcp FLAGS

ACK
Acknowledge flag—Indicates that the acknowledgment field of
a segment specifies the next sequence number the sender of
this segment is expecting to receive.

FIN
Finish flag—Used to clear connections.

PSH Push flag—Indicates the data in the call should be immediately
pushed through to the receiving user.

RST Reset flag—Indicates that the receiver should delete the
connection without further interaction.

SYN
Synchronize flag—Used to establish connections.

URG Urgent flag—Indicates that the urgent field is meaningful and
must be added to the segment sequence number.

understanding tcp flags
Tcpdump: Filter Packets with Tcp Flags