An architectural pattern is a general, reusable solution to a commonly occurring problem in software architecture within a given context. Architectural patterns are similar to software design pattern but have a broader scope. The architectural patterns address various issues in software engineering, such as computer hardware performance limitations, high availability and minimization of a business risk. Some architectural patterns have been implemented within software frameworks.
Even though an architectural pattern conveys an image of a system, it is not an architecture. An architectural pattern is a concept that solves and delineates some essential cohesive elements of a software architecture. Countless different architectures may implement the same pattern and share the related characteristics. Patterns are often defined as "strictly described and commonly available". When it is strictly described and commonly available, it is a pattern.
Following traditional building architecture, a 'software architectural style' is a specific method of construction, characterized by the features that make it notable" (Architectural style). "An architectural style defines: a family of systems in terms of a pattern of structural organization; a vocabulary of components and connectors, with constraints on how they can be combined."
"An architectural pattern is a named collection of architectural design decisions that (1) are applicable in a given development context, (2) constrain architectural design decisions that are specific to a particular system within that context, and (3) elicit beneficial qualities in each resulting system."
Some treat architectural patterns and architectural styles as the same, some treat styles as specializations of patterns. What they have in common is both patterns and styles are idioms for architects to use, they "provide a common language" or "vocabulary" with which to describe classes of systems.
The main difference is that a pattern can be seen as a solution to a problem, while a style is more general and does not require a problem to solve for its appearance.
Here is a list of architecture patterns, and corresponding design patterns and solution patterns.
Some additional examples of architectural patterns: