Block | If you block an account, they will no longer be able to follow your tweets and you will not receive a notification if they tweet your username.
Direct Message (DM) | Direct messages allow people on Twitter so send each other private messages. You can only send a Direct Message to someone you follow who follows you in return.
Discover | A column featuring content tailored to you based on who you follow.
#FF (Follow Friday) | Traditionally, people recommend Twitter accounts to follow on Fridays (hence Follow Friday!). If you see tweets with #ff at the beginning, the user is recommending accounts to follow.
Favourite | User can favourite a tweet either to store it for later reference or to indicate approval/support of a particular statement. Due to a recent change to the service, favourites can appear in the timeline of the people following you!
Hashtags | Prefixing a word with a ‘#’ turns a word into a ‘hashtag’. When clicking on a hashtag, you can view any other tweet using the same tag.
Lists | Lists are curated lists of other Twitter users, usually by topic or interest. Anyone can be added to a list and viewing a list enables you to see tweets only from those you have added to the list. You can also subscribe to other people’s lists.
Locked/Protected Accounts | Some people choose to lock their accounts so that they can engage with Twitter yet remain protected for whatever reason. It is considered bad etiquette to manually RT anything tweeted from a locked account (automatic retweets are disabled on locked accounts) without obtaining permission from the individual with a locked account.
Modified Tweet (MT) | When a user shares a tweet but modifies the content slightly. Used to flag that the tweet has been altered from the original.
Notifications | Column on Twitter where you can find any tweets mentioning your username, notification of any of your tweets that have been retweeted or favourited and when you have been added to lists or followed.
Report | Mechanism to report an individual for spam or abuse.
Retweet (RT) | A tweet that you forward to all of your followers. You can either just re-share the tweet as is, or you can add a comment to the tweet you are sharing (which will be embedded in your tweet).
Tweets | Short messages of 140 characters.