Issue type is not a custom field, it's a system field, and a structural one.
I would say Jack is right - for some reason, someone in your organisation has added an issue type called "job story". You'll need to ask them what it's for (and as it's lead to you questioning it, I'd recommend having a conversation about why they've used a name you had to question)
adding to the good suggestions of Nic and Jack I'd like to pass around the relevant sections of documentation in case you are interested in further reading.
This won't go into the detail as of the "why" there is a "Job Story" Issue Type present in your instance but it gives a nice overview about the terminology "Issue Type" and the differentiation to a Custom Field. Enjoy!
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