How can we bulk close issues on JIRA?

Here is how we can bulk close JIRAs

Step 1: Search all the issues/stories you wan to close (Using JQL or predefined filter of your own),  something like below.

Step 2: Choose the issues that needs to be closed.

Step 3: Choose Operation, Since we are closing, we need to select transition issues and go to next. 

Step 4: Choose the operation from available workflow actions

Step 5: Here I have choosed Resolved as i am closing these issues.

Step 6: Select Resolved and proceed further.

Step 7: Add comments (optional) and choose resolution

Step 8: Choose confirm to bulk close all the tickets.

Easy right!!

Epic v Stories vs Bugs

We have stories, epic and bug while creating an issue in JIRA system.

Here is difference between Epic v Stories vs Bugs

Epic:
An Epic can be defined as a big chunk of work that has one common objective. It could be a feature, customer request or business requirement. In backlog, it is a placeholder for a required feature with few lines of description. It tells compactly about final output of user needs. In the beginning, it may not contain all the details that team needs to work on. These details are defined in User Stories. An epic usually takes more than one sprint to complete.

User Stories
Epics are large user stories, typically ones which are too big to implement in a single iteration and therefore they need to be disaggregated into smaller user stories at some point. A user story is a very high-level definition of a requirement, containing just enough information so that the developers can produce a reasonable estimate of the effort to implement it

Bugs:
A software bug is an error, flaw, failure or fault in a program or system that causes it to produce an incorrect or unexpected result, or to behave in unintended ways based on the backlog or features in software cycle.
While communicating a bug, we need to make sure that a potential problem exists in the code that your team is developing. When you define a bug, you want to accurately report the problem in a way that helps the reader to understand the full impact of the problem. You should also describe the actions that you took to find the bug so that other members of the team can more easily reproduce the behavior. The test results should clearly show the problem. Clear, understandable descriptions affect the probability that the bug will be fixed.

Hope this helps!

Thanks