What is an institution?

From John Thompson’s Media & Modernity pg 13:

In some cases these positions acquire a certain stability by being institutionalized–that is, by becoming part of a relatively stable cluster of rules, resources and social relations. Institutions can be viewed as determinate sets of rules, resources and relations which have some degree of durability in time and some extension in space, and which are bound together for the purposes of pursuing some overall objectives. Institutions give a definite shape to pre-existing fields of interaction and, at the same time, they create new positions within these fields, as well as new sets of life trajectories for the individuals who occupy them.