OLTP stands for Online Transaction Processing, OLTP System deals with operational data. Operational Data is business transaction or activities which happen every day in the business i.e. In a banking system, you withdraw amount from your bank account, then withdrawal amount, available balance, account number, transaction number etc is operational data. In OLTP system, data is frequently inserted, updated and queried. OLTP system is most optimized to perform DML operation.
OLAP stands for Online Analytical Processing, OLTP System deals with historical data or archival data. OLAP systems are highly optimized for read operation. OLAP systems collects data over a period of time and store it in a very large database called Data Warehouse. This historical data is used for analysis purpose and to understand the trend of important KPI i.e. if we collect last 5 years of flight reservation data, then data can give us much meaningful information such as trends in reservation, peak reservation time, peak booking hours etc.