In the above picture, Wireshark does a great job of automatically highlighting the Flags field. There are a total of 8 flags in the 1 byte flags field, which are “set” by a 1 in the corresponding position.
For example, in this picture, the 1 is on the Synchronize bit, which means that this packet is a SYN.
At times you may see more than one bit set, as in the case of a SYN/ACK at the beginning of a TCP connection.