What are the practical uses of ontologies? I have read many papers and books about ontologies and I am trying to figure out that how they are used in a real project?

For example how the ontology for a soccer player robot can be defined and used with a cognitive architecture in order to make it intelligent?

Are ontologies relations between terms in that domain of knowledge ( for example relation between the ball and foot word and physical rules definition and their relation with the foot and ball movement , ...) or relations between tactics , strategies and different mixtures of tactics ?

Are there any clear examples of ontology usage in real projects and their combining usage with the cognitive architectures like ACT-R for augmenting the cognitive architecture?
I don't know about robotics, but ontologies are part of the standard toolkit for modern expert systems, especially those with a natural language processing component.

For example, consider the process of performing literature searches for systematic reviews in medicine. Of the millions of medical studies out there, reviewers need to find the 20 or so high-quality randomised control trial studies which are relevant to the clinical question that they want to answer. This is a classic needle-in-a-haystack problem, and computer scientists would like to build tools to aid the search.

Medical ontologies such as MeSH, ICD, and GALEN play a role in this, because they represent an "answer" to the question of what a given medical study is "about".