Segments are a filtering tool which allows you to specify a particular subset of your database.
You can combine filters to drill down and create a list of Contacts which meet your criteria.
The results will allow you to grab the information in order to send an email or SMS Campaign, to turn into an Autoresponder Sequence, or download the records as a CSV.
Building your Segment
To build a segment, filters are used to narrow down the Contacts you are searching for.
In the example below, the segment has two filters which will:
Find all people whose Position in their Organisation is "Career Advisor"
Find all people whose Status is "Current".
Once the "Save & Run" button is clicked, the segment will generate a list of applicable records:
To view the records, click the blue text. You'll then be able to view the list of Contacts. Click "Grab" to send the Contacts a Campaign, set up an Autoresponder, or download the data as a CSV.
FAQs
Q. What's the difference between AND and OR in segments?
A. AND is when you want to find all Contacts which match your filters. OR is for when you want to find Contacts which match one or the other of your filters.
Q. How do modify my segment after it's run?
A. Click the edit pencil to make any changes, then click "Save & Run" again.
Q. Do I have to click to edit even if I only want to check if anyone new has been added to the segment?
A. No. You only need to click the "refresh" icon: 
This will ensure you always have the latest records on the segment.
Q. I want to exclude Contacts whose emails don't work. How can I do this?
A. Use the condition 'People Email Verified Status is Failed":
Please note, this only works for a Contact's primary email address, not any secondaries.