JIRA query language (JQL) is a syntax used to help search for JIRA issues. Atlassian has an excellent full-length tutorial on JQL here, but some examples are as follows:

"Example 1: Return all issues that were made in the LCSET project in the last five days"

JQL Search: project = LCSET and created >= -5d

"Example 2: Return all issues in the SRS project that are currently in progress"

JQL Search: project = SRS and status = "In Progress" 

A more complicated example - the JQL behind the SRS board (as of 2/2018) is the following, and is saved in a filter called "SRS Production".

"Example 3: Return all issues that have no security level set and are in the projects LCSET, GAPREQ, PICO and XTR, and only if their status is Open. Exclude subtasks. Also show issues from the project SRS that do not have the status of Closed or Done, and don't show resolved SRS tickets that are older than 3 days."

JQL Search: level is

 EMPTY AND project in (LCSET, GAPREQ, PICO, XTR) AND type != Sub-task AND status in (open) OR project = "Sample Retrieval and Storage" AND (status not in (closed, done) OR resolved > -3d) ORDER BY Rank ASC