Twitter is a kind of public instant messenger stream. You go online or on your mobile device and send text messages (”tweets”) of up to 140 characters — or about one sentence long. Your tweets can be read by others, and you can sign up to follow the messages others write so that you can read theirs.
You can also add tags, which allow you to trace comments on particular subjects, events or stories.
a Wiki is a type of website that allows the visitors to add, remove, and sometimes edit the available content. This ease of interaction and operation makes a wiki an effective tool for collaborative authoring.