Exposures are based on the show records from our SnowFlake database. An exposure is logged when a template is loaded, it doesn't matter if a user saw it or didn't (e.g. in cases where the user would need to scroll the page in order to view the template).
In general, an exposure is logged when a template is loaded. Based on this logic if the page is refreshed, it will be counted as a new exposure.
Exposures can be logged separately using the /exposure/log API endpoint to ensure they are properly attributed to conversions.
On the other hand, an execution happens when the user meets the criteria of the effective pages and the user segmentation. An execution may be registered even if a user doesn't reach an Action card. An execution is registered after every pageview generated by a user. Repeat visits from the same user count as new executions.
Please note, that only the Show Newsletter Sign-up, Show Offer and Show Template action cards are captured. If a template is shown by the function tp.template.show() within a Run JS action card, the exposure won't be visible in the Composer reports.