Being in a Talent Pool will suggest you for jobs that match your skills and experience that you've shared in your profile.
You can be part of many of these Talent Pools for different companies. If you join the Open Market, you might even get suggestions for jobs from companies you hadn't thought about before.
When you're invited to join a Talent Pool, you'll get an email. Just click the 'Join Now' button in the email to become a member. And if you already have a profile, then you're all set once you join the Talent Pool.
For information on leaving a talent pool - please check out our help doc on that.