Multi-cluster virtual warehouses in Snowflake are designed to manage user and query concurrency needs. They allow for the allocation of additional clusters of compute resources, either statically or dynamically, to handle increased loads and reduce or eliminate the queuing of concurrent queries2.
https://docs.snowflake.com/en/user-guide/warehouses-multicluster.html#:~:text=Multi%2Dcluster%20warehous

Snowflake's virtual warehouses are responsible for query execution. They are clusters of compute resources that execute SQL statements, perform DML operations, and load data into tables

Explanation/Reference: https://interworks.com/blog/hcalder/2018/07/26/the-basics-of-loading-data-into-snowflake/

Snowflake credits are the unit of measure for the compute resources used in Snowflake. The number of credits consumed depends on the size of the virtual warehouse and the time it is running. Larger warehouses consume more credits per hour than smaller ones, and credits are billed for the time the warehouse is active, regardless of the actual usage within that time.
References: [COF-C02] SnowPro Core Certification Exam Study Guide