Agile Comparison with other methods

Agile methods are sometimes characterized as being at the opposite end of the spectrum from "plan-driven" or "disciplined" methods. This distinction is misleading, as it implies that agile methods are "unplanned" or "undisciplined". A more accurate distinction is that methods exist on a continuum from "adaptive" to "predictive". Agile methods lie on the "adaptive" side of this continuum.
Adaptive methods focus on adapting quickly to changing realities. When the needs of a project change, an adaptive team changes as well. An adaptive team will have difficulty describing exactly what will happen in the future. The further away a date is, the more vague an adaptive method will be about what will happen on that date. An adaptive team can report exactly what tasks are being done next week, but only which features are planned for next month. When asked about a release six months from now, an adaptive team may only be able to report the mission statement for the release, or a statement of expected value vs. cost.
Predictive methods, in contrast, focus on planning the future in detail. A predictive team can report exactly what features and tasks are planned for the entire length of the development process. Predictive teams have difficulty changing direction. The plan is typically optimized for the original destination and changing direction can cause completed work to be thrown away and done over differently. Predictive teams will often institute a change control board to ensure that only the most valuable changes are considered.
Agile methods have much in common with the "Rapid Application Development" techniques from the 1980/90s as espoused by James Martin and others.

Contrasted with other iterative development methods
Most agile methods share other iterative and incremental development methods' emphasis on building releasable software in short time periods. Agile development differs from other development models: in this model time periods are measured in weeks rather than months and work is performed in a highly collaborative manner. Most agile methods also differ by treating their time period as a strict timebox.

Contrasted with the waterfall model
Agile development has little in common with the waterfall model. As of 2008, the waterfall model is still in common use. The waterfall model is the most predictive of the methods, stepping through requirements capture, analysis, design, coding, and testing in a strict, pre-planned sequence. Progress is generally measured in terms of deliverable artifacts: requirement specifications, design documents, test plans, code reviews and the like.
The main problem with the waterfall model is the inflexible division of a project into separate stages, so that commitments are made early on, and it is difficult to react to changes in requirements. Iterations are expensive. This means that the waterfall model is likely to be unsuitable if requirements are not well understood or are likely to change in the course of the project.
Agile methods, in contrast, produce completely developed and tested features (but a very small subset of the whole) every few weeks or months. The emphasis is on obtaining the smallest workable piece of functionality to deliver business value early, and continually improving it/adding further functionality throughout the life of the project.
In this respect, agile critics incorrectly assert that these features are not placed in context of the overall project, concluding that, if the sponsors of the project are concerned about completing certain goals with a defined timeline or budget, agile may not be appropriate. Adaptations of Scrum show how agile methods are augmented to produce and continuously improve a strategic plan.
Some agile teams use the waterfall model on a small scale, repeating the entire waterfall cycle in every iteration.Other teams, most notably Extreme Programming teams, work on activities simultaneously.

Contrasted with "cowboy coding"
Cowboy coding is the absence of a defined method: team members do whatever they feel is right. Agile development's frequent re-evaluation of plans, emphasis on face-to-face communication, and relatively sparse use of documents sometimes causes people to confuse it with cowboy coding. Agile teams, however, do follow defined (and often very disciplined and rigorous) processes.
As with all development methods, the skill and experience of the users determine the degree of success and/or abuse of such activity. The more rigid controls systematically embedded within a process offer stronger levels of accountability of the users. The degradation of well-intended procedures can lead to activities often categorized as cowboy coding.