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.
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.