In SAP Analytics Cloud, dimensions usually represent qualitative master data. Product, cost center, and employee are all examples of dimensions. A model can, and typically does, have several dimensions.
A measure represents transactional or quantitative data; for example, price, revenue, number of customers. Measures are distinct from dimensions, so you can add and configure multiple measures with aggregation and units to fit your data.
In an account-based model, all the numeric values are stored in a single default dimension usually named Account, and you use the financial account structure to determine what each value represents. You can also add calculations, specify units, and set aggregation types for those values. Semantically, an Account dimension type may be referred to as a measure because it fulfills a similar purpose; however, it is really a dimension.

Note
A measure-based model also supports the account-based single measure dimension, but you can add other measures to the model as well. With the account-based model, you are limited to the single account-type dimension to represent measures.