OLAP – On-Line Analytical Processing.
Designates a category of applications and technologies that allow the collection,
storage, manipulation and reproduction of multidimensional data, with the goal of
analysis.

MOLAP – Multidimensional OLAP.
This term designates a cartesian data structure more specifically. In effect, MOLAP
contrasts with ROLAP. In the former, joins between tables are already suitable,
which enhances performances. In the latter, joins are computed during the request.
Targeted at groups of users because it’s a shared environment. Data is stored in an
exclusive server-based format. It performs more complex analysis of data.

DOLAP – Desktop OLAP.
Small OLAP products for local multidimensional analysis Desktop OLAP. There can be a mini multidimensional database (using Personal Express), or extraction of a
data cube (using Business Objects). Designed for low-end, single, departmental user. Data is stored in cubes on the desktop. It’s like having your own spreadsheet. Since the data is local, end users don’t have to worry about performance hits against the server.

ROLAP – Relational OLAP.
Designates one or several star schemas stored in relational databases. This
technology permits multidimensional analysis with data stored in relational
databases. Used for large departments or groups because it supports large amounts of data and users.

HOLAP: Hybridization of OLAP, which can include any of the above.