OLTP (Online Transaction Processing) describes the kind of data processing that deals with heavy transactional workloads. In OLTP workloads, in other words, there are many relatively simple, transactional operations (many reads and writes) constantly coming into the database. The data typically relates to standard business tasks like keeping track of inventory, hotel reservations, or online banking functions.
The other main kind of data processing is OLAP (Online Analytics Processing). Compared to OLTP workloads, the workloads run on OLAP databases are usually much more complicated but much less frequent.
Often, database technologies are designed with one or the other in mind. OLTP databases such as CockroachDB are focused on transactional use cases such as payment processing, logistics, metadata management – basically any use case that involves frequent reads and writes. OLAP databases, in contrast, are typically used for data analytics.
Often a company may use both, with the OLTP database handling the transactions coming from the application, and with relevant data periodically offloaded to an OLAP database for analysis. This approach ensures that even very complex analytics work will not interfere with the performance of the OLTP database.