fabric capacity

Hi Anonymous 
Thanks for using Fabric Community.

Fabric Capacity refers to the computational resources that power all experiences in Fabric. It’s measured in Capacity Units (CUs), which quantify the compute power available for a given SKU.
Microsoft Fabric Capacity Licenses: Your Guide for Growth and Success  - Applied Information Sciences (ais.com)

Here’s how it relates to your questions:

Data Ingestion:
Yes, the capacity is related to the amount of data you ingest into the warehouse/lakehouse. The size of the capacity determines the amount of capacity throughput, measured in Capacity Unit seconds (CUs), which can impact data ingestion.
Fabric Capacities – Everything you need to know about what’s new and what’s coming | Microsoft Fabric Blog | Microsoft Fabric

Scheduled Refreshes:
Yes, the capacity is also related to scheduled refreshes. If Fabric is turned off during low times to reduce costs, all of the dashboard schedule refreshes fail. You can monitor utilization to get the most out of your capacities.
Solved: Power BI Gateways and Refreshes with Fabric Capaci... - Microsoft Fabric Community
Evaluate and optimize your Microsoft Fabric capacity - Microsoft Fabric | Microsoft Learn

Power BI Data Usage:
Yes, Power BI data usage during scheduled refreshes is part of the capacity. Power BI Premium customers can utilize their Power BI Premium capacity for any of the new workloads.

If you need to increase the capacity, you can scale it up in the Azure portal.
Scale your Fabric capacity - Microsoft Fabric | Microsoft Learn

You can also monitor your capacities to understand what’s causing the high usage. For example, you can use the Capacity Metrics App to understand what is happening.
Solved: capacity limit exceeded - Microsoft Fabric Community
What is the Microsoft Fabric Capacity Metrics app? - Microsoft Fabric | Microsoft Learn

Hope this helps. Please let me know if you have any further questions.