**Primary Data:**
Primary data refers to the original data that is collected directly from the source for the first time by the researcher. It is specific to the research objective and is collected through various methods such as surveys, interviews, observations, experiments, etc. Primary data is considered to be more reliable and accurate as it is collected firsthand.

**Secondary Data:**
Secondary data refers to the data that has already been collected and published by someone else. It is not specific to the current research objective and is obtained from sources like books, journals, government reports, websites, etc. Secondary data is used to supplement primary data and provide a broader perspective on the research topic.

**Differences between Primary Data and Secondary Data:**

1. **Source:**
- Primary data is collected directly by the researcher from the original source.
- Secondary data is collected by someone else and made available for reference.

2. **Purpose:**
- Primary data is collected to fulfill the specific research objective of the study.
- Secondary data is collected for various purposes and may not be directly related to the current research objective.

3. **Reliability and Accuracy:**
- Primary data is considered to be more reliable and accurate as it is collected firsthand and can be tailored to the research needs.
- Secondary data may vary in reliability and accuracy depending on the source and the process through which it was collected.

4. **Time and Cost:**
- Primary data collection can be time-consuming and costly as it requires designing surveys, conducting interviews, or running experiments.
- Secondary data collection is relatively quicker and cost-effective as the data already exists and can be accessed easily.

5. **Control over Data:**
- In primary data collection, the researcher has full control over the data collection process and can ensure the quality and relevance of the data.
- In secondary data, the researcher has limited control over the data as it is already collected by someone else, and there may be limitations in terms of data availability and quality.

6. **Originality:**
- Primary data is original and unique to the research study.
- Secondary data is not original as it has been collected by someone else for a different purpose.

In conclusion, primary data is collected directly by the researcher for a specific research objective, while secondary data is pre-existing data collected by someone else. Both types of data have their own advantages and disadvantages, and researchers often use a combination of primary and secondary data to gain a comprehensive understanding of their research topic.