What is the meaning of this highlighted ticket and why can't we move this at the board vertically?

[Darcy M]

I find it weird that we can move all the other tickets vertically and horizontally within our boards except for tickets that are highlighted this way. 

Some of them are not tagged as high-priority and none of them are flagged so I am not entirely sure what it's for. Could anyone help and give some insights?

At first, I thought that it was because someone has a timer running on but it doesn't look like it. 

[Stephen_Lugton]

Hi @Darcy M 

That highlighted ticket is a sub-task of the ticket above it.

The priority of sub-tasks cannot be changed independent of the parent ticket which is why they cannot be moved vertically.

If the sub-tasks can't be moved horizontally it is possible that the statuses that are available to them haven't been mapped to the board since sub-tasks often have a different set of statuses to stories

For more information on sub-tasks see Understanding issue types in Jira