A collaboration tool is something that helps people collaborate

Collaboration

Collaboration is working together to achieve a goal. It is a recursive process where two or more people or organizations work together to realize shared goals, — for example, an intriguing endeavor that is creative in nature—by sharing...

. The term is often used to mean collaborative software

Collaborative software

Collaborative software is computer software designed to help people involved in a common task achieve goals...

, but collaboration tools were being used before computer

Computer

A computer is a programmable machine designed to sequentially and automatically carry out a sequence of arithmetic or logical operations. The particular sequence of operations can be changed readily, allowing the computer to solve more than one kind of problem...

s existed. A piece of paper

Paper

Paper is a thin material mainly used for writing upon, printing upon, drawing or for packaging. It is produced by pressing together moist fibers, typically cellulose pulp derived from wood, rags or grasses, and drying them into flexible sheets....

, for example, can be used as collaboration tool.

Everything that helps to solve a predefined task together in a group more easily is an effective collaborative tool.
Collaboration means, in this context, working together to fulfill a shared, collective, bounded goal.
Conference phone calls

Conference call

A conference call is a telephone call in which the calling party wishes to have more than one called party listen in to the audio portion of the call. The conference calls may be designed to allow the called party to participate during the call, or the call may be set up so that the called party...

 may be replaced by asynchronous conferencing

Asynchronous conferencing

Asynchronous conferencing is the formal term used in science, in particular in computer-mediated communication, collaboration and learning, to describe technologies where there is a delay in interaction between contributors...

, video conferences, IRC or Instant Messaging

Instant messaging

Instant Messaging is a form of real-time direct text-based chatting communication in push mode between two or more people using personal computers or other devices, along with shared clients. The user's text is conveyed over a network, such as the Internet...

 now.
Peer Review

Peer review

Peer review is a process of self-regulation by a profession or a process of evaluation involving qualified individuals within the relevant field. Peer review methods are employed to maintain standards, improve performance and provide credibility...

s of documentation are easier to establish through wiki

Wiki

A wiki is a website that allows the creation and editing of any number of interlinked web pages via a web browser using a simplified markup language or a WYSIWYG text editor. Wikis are typically powered by wiki software and are often used collaboratively by multiple users. Examples include...

s than by iterative versions on paper.
Whiteboard

Whiteboard

A whiteboard is a name for any glossy, usually white surface for nonpermanent markings. Whiteboards are analogous to chalkboards, allowing rapid marking and erasing of markings on their surface...

s are partly imitated by Online whiteboards that allow telework. Google Wave

Google Wave

Apache Wave is a software framework for real-time collaborative editing online. Google Inc. originally developed it as Google Wave.It was announced at the Google I/O conference on May 27, 2009....

is a collaborative tool.