Patrolling
Patrol types: A combat patrol is a group with sufficient size (usually platoon or company) and resources to raid or ambush a specific enemy.  It primarily differs from an attack in that the aim is not to hold ground.
A clearing patrol is a brief patrol around a newly occupied defensive position in order to ensure that the immediate area is secure. Clearing patrols are often undertaken on the occupation of a location, and during stand to in the transition from night to day routine and vice versa.
A standing patrol is a static patrol, probably known as an OP/LP(Observation Post/Listening post) in US and NATO terminology. Standing patrols are usually small (half section/section) static patrols intended to provide early warning, security or to guard some geographical feature, such as dead ground.
A reconnaissance (recce) patrol is a patrol, usually small whose main mission is the gathering of information. Generally speaking recce patrols tend to avoid contact, although it is not unknown for recon patrols to "fight for information".
A screening patrol combines a number of patrols to 'screen' a large area. This type of patrol is used by armored formations in desert theaters, and also by ground troops operating in urban areas. A screen is generally composed of a number of static observation posts.

See also: List of military tactics
Observation post
Maritime patrol

References: 

External links: 
Patrolling magazine, 75th Ranger Regiment Association