What is regression testing and sanity testing?

Regression Testing:

Whenever developers change or modify their software, even a small tweak can have unexpected consequences.  Testing existing software applications to make sure that a change or addition hasn’t broken any existing
functionality is called regression testing. Its purpose is to catch bugs that may have been accidentally introduced into a new build or release candidate, and to ensure that previously eradicated bugs continue to stay dead.

Sanity Testing:

After receiving a Software build with the minor issues fixes in code or functionality, Sanity testing is carry out to check whether the bugs reported in previous build are fixed & there
is regression introduced due to these fixes i.e. not breaking any previously working functionality. The main aim of Sanity testing to check the planned functionality is working as expected. Instead of doing whole regression testing the Sanity testing is perform.
- See more at: http://www.softwaretestingclass.com/sanity-testing/#sthash.ZtqGvqIX.dpuf After receiving a Software build with the minor issues fixes in code or functionality, Sanity testing is carry out to check whether the bugs reported in previous build are fixed & there
is regression introduced due to these fixes i.e. not breaking any previously working functionality. The main aim of Sanity testing to check the planned functionality is working as expected. Instead of doing whole regression testing the Sanity testing is perform.
- See more at: http://www.softwaretestingclass.com/sanity-testing/#sthash.ZtqGvqIX.dpuf After receiving a Software build with the minor issues fixes in code or functionality, Sanity testing is carry out to check whether the bugs reported in previous build are fixed & there
is regression introduced due to these fixes i.e. not breaking any previously working functionality. The main aim of Sanity testing to check the planned functionality is working as expected. Instead of doing whole regression testing the Sanity testing is perform.
- See more at: http://www.softwaretestingclass.com/sanity-testing/#sthash.ZtqGvqIX.dpuf After receiving a Software build with the minor issues fixes in code or functionality, Sanity testing is carry out to check whether the bugs reported in previous build are fixed & there
is regression introduced due to these fixes i.e. not breaking any previously working functionality. The main aim of Sanity testing to check the planned functionality is working as expected. Instead of doing whole regression testing the Sanity testing is perform.
- See more at: http://www.softwaretestingclass.com/sanity-testing/#sthash.ZtqGvqIX.dpuf After receiving a Software build with the minor issues fixes in code or functionality, Sanity testing is carry out to check whether the bugs reported in previous build are fixed & there
is regression introduced due to these fixes i.e. not breaking any previously working functionality. The main aim of Sanity testing to check the planned functionality is working as expected. Instead of doing whole regression testing the Sanity testing is perform.
- See more at: http://www.softwaretestingclass.com/sanity-testing/#sthash.ZtqGvqIX.dpuf After receiving a Software build with the minor issues fixes in code or functionality, Sanity testing is carry out to check whether the bugs reported in previous build are fixed & there
is regression introduced due to these fixes i.e. not breaking any previously working functionality. The main aim of Sanity testing to check the planned functionality is working as expected. Instead of doing whole regression testing the Sanity testing is perform.
- See more at: http://www.softwaretestingclass.com/sanity-testing/#sthash.ZtqGvqIX.dpuf After receiving a Software build with the minor issues fixes in code or functionality, Sanity testing is carry out to check whether the bugs reported in previous build are fixed & there
is regression introduced due to these fixes i.e. not breaking any previously working functionality. The main aim of Sanity testing to check the planned functionality is working as expected. Instead of doing whole regression testing the Sanity testing is perform.
- See more at: http://www.softwaretestingclass.com/sanity-testing/#sthash.ZtqGvqIX.dpuf After receiving a Software build with the minor issues fixes in code or functionality, Sanity testing is carry out to check whether the bugs reported in previous build are fixed & there is regression introduced
due to these fixes i.e. not breaking any previously working functionality. The main aim of Sanity testing to check the planned functionality is working as expected. Instead of doing whole regression testing the Sanity testing is perform.

Difference:

Sanity Testing	Regression Testing
1. Sanity testing is a surface level testing where QA engineer verifies that all the menus, functions and commands available/presented in the product are working fine.	1. Regression testing is not a surface level testing.
2. Sanity testing is considered as a subset of regression testing.	2. Regression testing is not considered as a subset of any.
3. This testing is performed/executed when testers have not much/enough time for doing testing.	3. This testing is performed/executed when tester’s have enough time for testing.
4. Sanity testing is usually conducted manually not by using any automation tools.	4. Regression testing may be conducted/consider manually or using automated tools.
5. Performing this type of testing will not enlarge the product/project cost and budget because it didn't require much manpower and time.	5. Performing this type of testing definitely will enlarge the product cost and budget because it requires more manpower and time.
6. Not complete test cases are executed/ performed in the product during sanity testing.	6. During this testing complete test cases are executed/ performed in the product.
7. During this testing tester test the application or product with finer details.	7. During this testing tester test the application or product with more details.
8. We do not use script for sanity testing.	8. We use script for regression testing.