An ID variable is a type of variable that can store an ID value of a record or a record type in a flow. It can be used to store the ID of a record type for later use in a flow, such as assigning it to a record or using it in a condition. A boolean variable is a type of variable that can store a true or false value in a flow. A text variable is a type of variable that can store a text value in a flow. A record variable is a type of variable that can store one or more field values of a record in a flow. References: https://help.salesforce.com/s/articleView?id=sf.
flow_ref_elements_variables.htm&type=5