Question: What does it mean when you say I can receive digest or regular posts?
Answer: Most mailing lists have this option. Regular posts are simply when you receive each individual message from someone as they send it. Digest posts are when you get a bunch of posts put together into one message, usually once a day.
The advantages of getting regular posts are: easier to see who wrote what, when you respond to a message it gives you the correct subject and address lines, you will see posts faster, you can quickly delete posts you aren't interested in. People who read most of the posts of a mailing list and respond a lot tend to prefer the regular setting.
The advantages of getting the digest are: fewer total messages per day, you can skim one message and delete a bunch of posts in one fail swoop. People who are just skimming a list for an occasional interesting post tend to prefer the digest setting.
Ultimately, whether or not you choose digest or regular is a matter of personal preference.