A List is a curated group of Twitter accounts. You can follow Lists created @MertonTV. Viewing a List timeline will show you a stream of Tweets from only the accounts on that List.
This can be particularly helpful during a localised incident or Council Meeting where you may gain a better insight into things that are happening.
For example, during a Full Council meeting a number of accounts may describe what is happening from their points of view, additional data, documents may be linked to. You may also spot completely unrelated tweets that could suggest that some people may not be giving the full attention a matter should receive. You may not want to naturally follow all accounts yourself within the list, but having additional accounts forms a better timeline of events to see when a random RT may have been sent during an important vote.
Using the above Twitter Lists is a great way of quickly identifying comments, avoids having your own timeline flooded in Liverpool Football Club news or photos of Keo Beer. Perhaps you need to be in the right mindset to read some of the tweets, take the relevant medication before reading them. It also paints a cross-party picture of events, often highlighting similarities in things that probably did happen, and in the absence of supporting evidence from other parties, some tweets that probably are not the full truth.