OLAP - Online Analytical Processing, which deals with
analysis of data. It has to deal with historical data too (
for analysis purpose) Not updated frequently. If required
bulk update is allowed. 

OLTP - Online Transactional Processing, which deals with
transactions. For e.g. withdrawals at ATM machines. It
involves many transactions. The databases have to be updated
more frequently after the successful completion of a
transaction.

i am agree with the above answer.olap is denormalized and
oltp normalised

OLTP 
* Is the E-R modleling,there are more concurrent users,
* It contains normalized tables so there is no redundancy.
* More tables,Joins and less Indexes,
* It stores daily transactional data
* It stores very less data 
* It contains mainly current data
* INSERT,UPDATE,MODIFY can be applied on OLTP.
* Performace will be high

OLAP
* It is the Dimensional Modeling
* It contains Denormalised  tables there will be redundancy.
* Less tables,Joins and more Indexes
* It stores operational data
* It contains Historical and Present data
* only SELECT clause is applied on OLAP
* It stores very Huge data
* Performance will be low compared with OLTP