@ = Reply: Use this to address a public message to a user.
RT – Retweet: This indicates a posting is a retweet from another user.
DM – Direct Message: You can only send a direct message to someone who is following you.
# – Hashtag: Used to categorize tweets and keeps tweets grouped together.
Like: This allows other users to know if you appreciate a particular post.
Poke: A way to interact with friends and has flirting connotations. Avoid in business matters.
Status: A microblogging feature to inform other users of your actions and thoughts.
Tag: Marks a photo or video with text to identify a person.
You Tube
Like: YouTube users have the ability to vote videos up or down with the like or unlike buttons.
View: Usually refers to viewer count, which keeps a record of the number of views a video receives.
Google+
Circle: A categorization system for friends and followers.
Green: When a post is marked with a green button it is public.
Blue: When a post is marked with a blue button, it is only for people in your circles.
Hangout: A group video chat feature for users in your circle.
Tumblr
Dash: Short for dashboard, it is the main news feed of Tumblr blogs you follow.
Heart: Users can like posts by clicking on the heart above the post in their dash.
Tag: Categorization system for posts that allows users to find new blogs.
Reblogz Users can reblog posts they enjoy to their own blog.
Digg
Digg: Refers to users liking a post.
Top News: The main page of Digg that shows the most shared posts on Digg.
