There are two types of skills: standard skills and interaction property skills.
A standard skill is simply a label, such as Basic Tech, that is assigned to a topic. To handle the questions within that topic will require the agent to also be assigned the standard skill.
Interaction property skills are based on a specific value for an interaction property. For instance, an interaction property named Operating System might have three possible values – Windows, Mac, and Linux. If a skill is created that references a value for this property (e.g., Mac), then any message within any topic that has that interaction property value (e.g., Mac) will only be routed to the agents that have this skill assigned. Skills that are based on interaction properties are NOT assigned to topics. They are only assigned to agents. The values for the interaction property itself are assigned to the question using filters or are set by the contact when the question is submitted.