New transitions do not have any conditions by default. This means that anyone who has access to the issue will be able to execute the transition. By adding a condition to a workflow transition, you can control who or when an issue can be transitioned.

Jira allows you to add any number of conditions to the transition:

1. Select the transition you want to add conditions to.
2. Click on the Conditions link.
3. Click on the Add condition link. This will bring you to the Add Condition To transition page, which lists all the available conditions you can add.
4. Select the condition you want to add.
5. Click on the Add button to add the condition.
6. Depending on the condition, you may be presented with the Add Parameters To Condition page, where you can specify the configuration options for the condition. For example, the User Is In Group condition will ask you to select the group to check against.

Newly added conditions are appended to the end of the existing list of conditions, creating a condition group. By default, when there is more than one condition, a logical AND is used to group the conditions. This means that all conditions must pass for the entire condition group to pass. If one condition fails, the entire group fails, and the user will not be able to execute the transition. You can switch to use a logical OR, which means only one of the conditions in the group needs to pass for the entire group to pass. This is a very useful feature as it allows you to combine multiple conditions to form a more complex logical unit.

For example, the User Is In Group condition lets you specify a single group, but with the AND operator, you can add multiple User Is In Group conditions to ensure the user must exist in all the specific groups to be able to execute the transition. If you use the OR operator, then the user will only need to belong to one of the listed groups. The only restriction to this is that you cannot use both operators for the same condition group.