Difference between Wireshark and Packet Tracer?

Packet Tracer doesn't capture packets, it's a virtualized tool created by Cisco to practice routing and switching. Mainly Cisco NetAcad students use it. It's comparable to GNS3.

Packet Tracer's traffic simulation tools are similar to Wireshark in the sense that you can click on a PDU (in this case, an envelope) and look at the bytes in the message as well as the decoded meaning of the message at the different layers of the stack, but that's really as far as the similarities go.

Packet Tracer is not only not a real network, but it's not a virtualized network either, at least not in the same sense as something like GNS3 (which can run real Cisco IOS and create real packets, even those leaving a physical network card). Packet Tracer is limited to its own sandbox and exists solely for training purposes, whereas Wireshark has a greater scope. Wireshark can look at "real" packets from actual networks, both from a network card directly or saved/distributed in a standardized packet capture file format. In short, Wireshark's scope extends to the real world, and the real network administration workforce, whereas Packet Tracer is a classroom training tool.